Remove race condition while deleting groups

## What does this MR do?

The intended flow during a group deletion is:

```
  Soft-delete group (sync) -> Delete group projects (async) -> Hard-delete group (async)
```

The soft-delete was run in a transaction, which was committed only after
the async job (for hard-deletion) was kicked off. There was a race
condition here - the soft-delete transaction could complete _after_ the
hard delete completed, leaving a soft-deleted record in the database.

This MR removes this race condition. There is no need to run the
soft-delete in a transaction. The soft-delete completes before the async
job is kicked off.

This MR also adds a migration to delete all existing (soft-deleted) groups left in an inconsistent state
due to this bug.

- Closes #23223 
- EE merge request: gitlab-org/gitlab-ee!886

See merge request !7528

Fix Admin Links to new Group does not respect Default Visibility

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19981

See merge request !7560

Add changelog entry for 7251

See merge request !7543

Pipelines page redesign

Closes #23637
![Screen_Shot_2016-11-15_at_1.36.34_PM](/uploads/edc6a58f00cca3e03ffd1689bd6eebd8/Screen_Shot_2016-11-15_at_1.36.34_PM.png)

See merge request !7487

Settings

This is done by passing a visibility_level option to the group edit _form.
The visibility_level is set to @group.visibility_level in edit ation and
to default_group_visibility in the new action.

Grapify repository api

See merge request !7534

Use the public CE repo URL instead of the one used in the runner

See the commit message to understand the reason of this change.

See merge request !7555

Allow registering users where the username contains dots (.)

## What does this MR do?

- Allow registering users whose usernames contains dots `.`
- This can currently be done by registering with a username containing no dots, and then editing the username to have dots in the user's profile settings.

## Does this MR meet the acceptance criteria?

-  [#24276/!7500] Unable to register names with dot
    - [x]  Implementation
    - [x]  Tests
        - [x]  Added
        - [x]  [Passing](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7500/builds)
    - [x]  Meta
        - [x]  CHANGELOG entry created
        - [x]  Documentation created/updated
        - [x]  API support added
        - [x]  Branch has no merge conflicts with `master`
        - [x]  Squashed related commits together
    - [x]  Review
        - [x]  Endboss
            - [x]  Use `Gitlab::Regex::NAMESPACE_REGEX_STR` instead of a hardcoded pattern
            - [x]  Define `NAMESPACE_REGEX_STR` in terms of `NAMESPACE_REGEX_STR_JS`
    - [ ]  Wait for merge


## What are the relevant issue numbers?

- Closes #24276

See merge request !7500

Check all namespaces on validation of new username.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24519 and https://gitlab.com/gitlab-org/gitlab-ce/issues/24580

See merge request !7537

- Use multiple threads / database connections to:

  1. Escape the transaction the spec seems to be running
     in (`config.use_transactional_fixtures` is off, but
     `ActiveRecord::Base.connection.open_transactions` is not empty
     at the beginning of the spec.

  2. Simulate a Sidekiq worker performing the hard delete outside of the
     soft-delete transaction.

- The spec is a little clunky, but it was the smallest thing I could get
  working - and even this took a couple of hours. Let me know if you
  have any suggestions to improve it!

The intended flow is:

  Soft-delete group (sync) -> Delete group projects (async) -> Hard-delete group (async)

The soft-delete was run in a transaction, which was committed only after
the async job (for hard-deletion) was kicked off. There was a race
condition here - the soft-delete transaction could complete _after_ the
hard delete completed, leaving a soft-deleted record in the database.

This commit removes this race condition. There is no need to run the
soft-delete in a transaction. The soft-delete completes before the async
job is kicked off.

The database should not have any soft-deleted groups. Due to a race
condition (soft-delete completes after the hard-delete), soft-deleted
groups were (incorrectly) left in the database, causing issues while
trying to create a new group with the same name.

Fix wrong link URL

See merge request !7554

[ci skip]

Grammar fix in environments.md: s/base/basis

See merge request !7552

[ci skip]

[ci skip]

[ci skip]

[ci skip]

[ci skip]

Javascript does not support the negative lookbehind assertion (?<!) used
in the Ruby regex (to disallow usernames ending in `.git` or `.atom`.

Getting the client side code to fully support this format is
non-trivial, since we'd either have to heavily complicate the
regex used, or modify the frontend code to support more complex
validation schemes (it currently uses HTML5 validations).

The pragmatic choice is to create a
`Gitlab::Regex::NAMESPACE_REGEX_STR_SIMPLE` regex to serve as a
Javascript-compatible version of `NAMESPACE_REGEX_STR`.

The client-side code will not display an error for usernames ending in
`.git` and `.atom`, but these will be caught by the server-side
validation.

bump rouge to 2.0.7

## What does this MR do?
Upgrades Rouge to 2.0.7 for various bugfixes.

## Are there points in the code the reviewer needs to double check?
See the Rouge changelog here: https://github.com/jneen/rouge/blob/v2.0.7/CHANGELOG.md

See merge request !7549

CHANGELOG: https://github.com/jneen/rouge/blob/v2.0.7/CHANGELOG.md

Resolve "Create a tab shortcut to jump directly to content"

## What does this MR do?
Adds accessibility shortcut to page, i.e. if user hits `tab` key right after the page is loaded and user has not interacted to any part of the page, the shortcut appears at top left corner of the page. Then, pressing `enter` (`spacebar` support is WIP) scrolls page to focus on content.

## Are there points in the code the reviewer needs to double check?
See if `id` attribute added to `.content` element (present in [_page.html.haml](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/layouts/_page.html.haml)) needs to be reviewed if it is correct approach or we already have an ID that shortcut can refer to.

## Why was this MR needed?
This feature is particularly useful for screen readers where user doesn't have to go through entire nav to reach content of page.

## Screenshots (if relevant)
![Screenshot_from_2016-11-17_17-59-22](/uploads/0eb0149f46bd35e9ce629e7a6533be53/Screenshot_from_2016-11-17_17-59-22.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #24057

See merge request !7533

Add placeholder in the color input inside the create new label popup

## What does this MR do?
Adds the missing placeholder  *"Assign custom color #FF0000"*  in the label creation popup ( example text for custom hex color).

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?
When creating a new label, the example text for custom hex color is missing

## Screenshots (if relevant)
Before
![before](/uploads/a3157414d59cea609118a7d711f9b9ee/before.png)

After
![Selection_051](/uploads/ca3e2089b40069e4cb6b7aa295b28cfc/Selection_051.png)

## Does this MR meet the acceptance criteria?

- [X] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#24512 

See merge request !7492

Improve importing of github pull requests

Closes #24072

See merge request !7241

Update "Supported web browsers" text

## What does this MR do?

Updates the `Supported web browsers` text in the installation docs.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Slack discussion

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !7341

Allow sorting groups in API

Relates to #20013.

See merge request !7529

Update copy.md with issue guideline updates and merge request guidelines

Update copy.md with issue guideline updates and merge request guidelines

See merge request !7513

Update examples and labels to use sentence case.

Update copy.md  [ci skip]

Update copy.md [ci skip]

Update copy.md

Ref #24073

Fix missing URL from environments docs

See merge request !7542

[ci skip]

Fix line numbers not matching up with code in Firefox.

Firefox has had broken line number alignment for a while now, if this is a bug with Firefox they don't seem to want to fix it since its been there from 46 through 49. This fixes it.

Before:

![Screen_Shot_2016-09-22_at_3.08.44_PM](/uploads/8bb65f40e44f738c0c375b0c8ef7dea6/Screen_Shot_2016-09-22_at_3.08.44_PM.png)

After:

![Screen_Shot_2016-09-22_at_3.09.10_PM](/uploads/9e537be56886569d8a82390f2b97c42b/Screen_Shot_2016-09-22_at_3.09.10_PM.png)

Fixes #20202.

Safari/Chrome work the same as before, Snippets seems to work fine still as well.

Page tested: http://localhost:3000/gitlab-org/gitlab-ce/blob/master/app/models/project.rb

cc: @annabeldunstone

See merge request !6485