Bring back "notification-dropdown" class for styling and use "js-notification-dropdown" for JavaScript

Enable Style/MultilineOperationIndentation in Rubocop

Fixes #25741

See merge request !8125

Mattermost session

This branch is based of tag v8.14.4 so I could test on an instance better.

But stuck on the tests, as setting up the whole doorkeeper stuff doesn't seem to be supported for testing.

See merge request !8033

Cleaner merge commit messages

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23462

See merge request !7722

Add sorting functionality for group/project members

## What does this MR do?

This MR adds sort functionality to group/project members list.

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

No.

## Why was this MR needed?

This MR helps the user to manage and find users of a group/project fast. It also improves UX.

## Screenshots (if relevant)

**Before**
![before-pr-member](/uploads/412bfdfddc63e48a62e2095d664660b5/before-pr-member.png)

**After**
![pr-after](/uploads/ae23a5c7689b46d26a948f22a0ac2360/pr-after.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] 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?

Closes #21622 


Closes #23573

See merge request !7032

Avoid use of Hash#dig to keep compatibility with Ruby 2.1

See merge request !8153

Refactor Bitbucket importer to use BitBucket API Version 2

## What does this MR do?

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

## Why was this MR needed?

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/19946

## Screenshots (if relevant)

This MR needs the following permissions in the Bitbucket OAuth settings:

![image](/uploads/a26ae5e430a724bf581a92da7028ce3c/image.png)

- [] 

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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 [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5995

Resolve "Clean up CSS for project alerts and flash notifications."

## What does this MR do?

Cleans up CSS and html for alert stripes at the top of project pages.

## Screenshots

#### Before:

![Screen_Shot_2016-12-16_at_2.39.01_PM_copy](/uploads/6a700cf1e41557c00cdaef40f6a2a5b2/Screen_Shot_2016-12-16_at_2.39.01_PM_copy.png)

#### After:

![Screen_Shot_2016-12-16_at_2.39.23_PM_copy](/uploads/c849578becc3a634e8b15ab5340d86a2/Screen_Shot_2016-12-16_at_2.39.23_PM_copy.png)

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

In order to get multiple alerts to appear manually while testing, I simply added the following block to [app/views/shared/_no_password.html.haml](app/views/shared/_no_password.html.haml):

```

.no-password-message.alert.alert-warning.hidden-xs
  You won't be able to pull or push project code via #{gitlab_config.protocol.upcase} until you #{link_to 'set a password', edit_profile_password_path} on your account

  .pull-right
    = link_to "Don't show again", profile_path(user: {hide_no_password: true}), method: :put
    |
    = link_to 'Remind later', '#', class: 'hide-no-password-message'

.no-password-message.alert.alert-warning.hidden-xs
  You won't be able to pull or push project code via #{gitlab_config.protocol.upcase} until you #{link_to 'set a password', edit_profile_password_path} on your account

  .pull-right
    = link_to "Don't show again", profile_path(user: {hide_no_password: true}), method: :put
    |
    = link_to 'Remind later', '#', class: 'hide-no-password-message'

.no-password-message.alert.alert-warning.hidden-xs
  You won't be able to pull or push project code via #{gitlab_config.protocol.upcase} until you #{link_to 'set a password', edit_profile_password_path} on your account

  .pull-right
    = link_to "Don't show again", profile_path(user: {hide_no_password: true}), method: :put
    |
    = link_to 'Remind later', '#', class: 'hide-no-password-message'
```


## Why was this MR needed?

More alert-warning stripes are coming via the CI usage limits implementation in EE (https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/965), and these layout margins and colors were becoming messy.

## 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~~
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] 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)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #25743

See merge request !8151

Make autocomplete request performant

## What does this MR do?

Restricts the `autocomplete_sources`action to returning the `json`of one specific `at` type at a time.

Makes sure all commands start by immediately showing the `loading` dropdown.

If the `loading` dropdown is active, we will request and load in the data for that specific `at` type. We manually trigger the filter again. This time, if `loading` dropdown is not active, initiate default filter behaviour and use the correct data template.

Also fixes an issue where `setup` was called multiple times by only setting up and destroying atwho on a focused/blured input.

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

## Why was this MR needed?

`autocomplete_sources` was requested on page load and is large.

## Screenshots (if relevant)

3 requests for 3 different first-time references.

![Screen_Shot_2016-10-14_at_14.43.12](/uploads/0b04eab0d0bf3638d6d6e431036b8089/Screen_Shot_2016-10-14_at_14.43.12.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] 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)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #22802

Closes #18435

See merge request !6856