Allow the Rails cookie to be used for API authentication

Makes the Rails cookie into a valid authentication token for the Grape
API, and uses it instead of token authentication in frontend code that
uses the API.

Rendering the private token into client-side javascript is a security
risk; it may be stolen through XSS or other attacks. In general,
re-using API code in the frontend is more desirable than implementing
endless actions that return JSON. 

Closes #18302

See merge request !1995

[ci skip]

The practical effect of this commit is to make the API check the Rails session
cookie for authentication details. If the cookie is present and valid, it will
be used to authenticate.

The API now has several authentication options for users. They follow in this
order of precedence:

* Authentication token
* Personal access token
* OAuth2 Bearer token (Doorkeeper - application access)
* Rails session cookie

The `guard_all!` method is never called, and `guard!` is not implemented. The
`doorkeeper_guard!` method is also never called, and is mostly the same as its
non-bang counterpart.

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

Increase ci_builds artifacts_size column to 8-byte integer to allow larger files

See merge request !6333

Integer migration style

See merge request !6334

Add link to article on how to write reliable, asynchronous tests with Capybara

This article has been incredibly useful for all developers. Adding a link to it so more people can refer to it.

See merge request !6312

Hides tooltip on discussion toggle button when clicking

## What does this MR do?

Hides the tooltip when clicking the discussion toggle button.

Rather than triggering the tooltip to hide we trigger blur. This is because of how _amazing_ Bootstraps tooltips are. They are shown also on focus so if we trigger the tooltip to hide & then mouseover the button again the tooltip still shows. 

## What are the relevant issue numbers?

Closes #20750

See merge request !6303

Fixed issue boards loading issues on large screens

## What does this MR do?

On larger screens it is possible for 20 issues to load (this is the amount per page) & there still to be room underneath the last issue which means the list can't scroll stopping the infinite scrolling working.

This MR checks if there are more issues to load, if there are & the height of the scroll area is less than or the same as scroll height then more issues are loaded. This will keep happening until it is possible to scroll, once it is possible to scroll it goes back to the default behaviour of the infinite scrolling.

## What are the relevant issue numbers?

Closes #22092

See merge request !6319

Fix issuable templates dropdown for forked projects

fixes #21824

See merge request !6329

Added group-specific setting for LFS.

Groups can enable/disable LFS, but this setting can be overridden at the project level. **Admin only**

Closes #18092

See merge request !6164

Bump rubocop-rspec to 1.7.0

See merge request !6357

Fix spelling: sucessfully -> successfully

Originally from gitlab-org/gitlab-ee!682

See merge request !6376

Sort secret keys by key instead of id.

Closes #20870 

See merge request !6275

Fix undefined method when reverting migration `RemoveProjectsPushesSinceGc`

See merge request !6375

CI stages

#### What does this MR do?
Removes individual columns for each stage, consolidating them into one `Stages` column

#### Screenshots (if relevant)
![Screen_Shot_2016-09-14_at_12.32.41_PM](/uploads/24f8d817481ba8f711c127bf143649ba/Screen_Shot_2016-09-14_at_12.32.41_PM.png)

#### What are the relevant issue numbers?
Closes  #21925

See merge request !6338

Originally from gitlab-org/gitlab-ee!682

Added keyboard shortcut to navigate to issue boards

## What does this MR do?

Adds a keyboard shortcut of `g l` to navigate to issue boards.

`g b` would work nicer. However that is taken by builds. Open to suggestions.

## What are the relevant issue numbers?

Closes #21218

See merge request !6248

Update snippets UI

## What does this MR do?

Updates snippets UI _(mainly mobile view)_ to new UI proposed in #18849.

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

Does anyone know the implementation difference between `app/views/snippets/show.html.haml` and `app/views/projects/snippets/show.html.haml`? I have only been updating the latter as it's the only one I can find implemented. I assume the former is rendered somewhere seeing as there is controllers for it too. But this doesn't seem very DRY from my current perspective.

## Why was this MR needed?

## Screenshots (if relevant)

![Screen_Shot_2016-09-06_at_14.20.10](/uploads/ac124a3b0896872ce851b9f56fbe339c/Screen_Shot_2016-09-06_at_14.20.10.png)

![Screen_Shot_2016-09-06_at_14.20.32](/uploads/8d3c7b1d1a5f562ceb6dc22bde695289/Screen_Shot_2016-09-06_at_14.20.32.png)

![Screen_Shot_2016-09-06_at_14.20.48](/uploads/6b1c31ece6d2400bbfc3c673d9e82d4b/Screen_Shot_2016-09-06_at_14.20.48.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 [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 you do - 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 #18849

See merge request !6210

Restore gl_dropdown.js changes

Restores `fieldName` to allow only string values. `fieldName` was changed to accept  function as a value in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/581 Since the approach changed in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/687 there's no need to accept function as value.

Backport changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/687

EE Issue: https://gitlab.com/gitlab-org/gitlab-ee/issues/919

See merge request !6234

Added wait for vue helper

Closes #21218

Reduce duplication in `Commits::{CherryPickService,RevertService}`

## What does this MR do?

This factorize similar code from `Commits::{CherryPickService,RevertService}`.

## Why was this MR needed?

To get rid of flay offense.

## What are the relevant issue numbers?

Closes #22203

See merge request !6366