Set KRB5 as default clone URL when Kerberos is enabled and user is logged in

_Originally opened at !363 by @cernvcs._

- - -

In GitLab instances where Kerberos authentication (gitlab-org/gitlab-ee!6) is enabled, this protocol becomes the preferred one.

This merge request extends the functionality provided in gitlab-org/gitlab-ee!70 where Kerberos url is displayed alongside the SSH and HTTP urls when Kerberos authentication is enabled.

The implementation proposed here makes Kerberos the default clone procotol when Kerberos is enabled. When a logged in user visits the main page for a project or creates a new one, the first url offered is the Kerberos one.

This merge request also aligns the [implementation](https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/helpers/button_helper.rb) and [usage](https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/views/shared/_clone_panel.html.haml) of the 3 clone buttons, adds additional tests and updates some others to consider all the possible scenarios.

See merge request !372

This removes several Spinach features and step definitions

Updated EE changelog for 8.7.2

See merge request !373

[ci skip]

[ci skip]

[Elastic][Fix] Database indexer skips invalid repos

https://gitlab.com/gitlab-org/gitlab-ee/issues/378

See merge request !353

Geo: Merge requests on Secondary should not check mergeable status

In a secondary Geo (#76) node, database is read-only. 

If you update your merge request and don't visit the primary node, you would end up with an unchecked `merge_status`.
We should not try to solve that in a secondary node, as this will lead to a 500 error because we can't update data on database.

This MR Fixes that:

```
Started GET "/root/test-project/merge_requests/1" for 189.101.232.69 at 2016-04-28 11:37:28 -0400
Processing by Projects::MergeRequestsController#show as HTML
  Parameters: {"namespace_id"=>"root", "project_id"=>"test-project", "id"=>"1"}
Completed 500 Internal Server Error in 372ms (ActiveRecord: 26.9ms)

ActionView::Template::Error (PG::ReadOnlySqlTransaction: ERROR:  cannot execute UPDATE in a read-only transaction
: UPDATE "merge_requests" SET "merge_status" = $1 WHERE "merge_requests"."id" = $2):
    39:     = render "projects/merge_requests/show/how_to_merge"
    40:     = render "projects/merge_requests/widget/show.html.haml"
    41:
    42:     - if @merge_request.source_branch_exists? && @merge_request.mergeable? && @merge_request.can_be_merged_by?(current_user)
    43:       .light.prepend-top-default
    44:         You can also accept this merge request manually using the
    45:         = succeed '.' do
  app/models/merge_request.rb:122:in `call'
  app/models/merge_request.rb:122:in `block (2 levels) in <class:MergeRequest>'
  app/models/merge_request.rb:272:in `check_if_can_be_merged'
  app/models/merge_request.rb:297:in `mergeable?'
  app/views/projects/merge_requests/_show.html.haml:42:in `_app_views_projects_merge_requests__show_html_haml__3632812159035673711_50958700'
  app/views/projects/merge_requests/show.html.haml:1:in `_app_views_projects_merge_requests_show_html_haml___4126596802437062695_51012840'
```

See merge request !366

Fix MR notifications for slack and hipchat when approvals are fullfiled

A Slack notification comes in after opening a MR about the MR being opened but it also comes in after a MR gets the minimum number of approvers and it uses the same message.

Same behavior is present in hipchat notifications.

Fixes #462

See merge request !325

CE upstream



See merge request !361

Geo: fix Geo::ScheduleRepoMoveService autoload error

While refactoring !354 (Geo: #76) missed class renaming. This will fix:

```
LoadError: Unable to autoload constant Geo::ScheduleRepoMoveService, expected /opt/gitlab/embedded/service/gitlab-rails/app/services/geo/schedule_repo_move_service.rb to define it
```

See merge request !364

Changes support from IE 10+ to IE 11+

IE 11 was released 17 October 2013; 2 years ago. Generally what I have experienced is that support for browsers (when newer ones are available) continues for up to 2 years. Based on that info we would drop support for IE 10 and the latest IE we would support would be IE 11. 

I also think this is more realistic since no one is really testing anything on IE 10 at the moment.  We should start testing on all the browser that we currently support. 

Also we can then have real support for flexbox and not need things like `-ms-flexbox` and other IE specific hacks. 

cc @iamphill @annabeldunstone @elvongray @alfredo1 @rspeicher 

See merge request !3913

Add letter_opener_web gem

Sent emails in the development environment will no longer automatically
be opened in the browser. If a sent email needs to be viewed, it can be
found at the `/rails/letter_opener` route.

See merge request !3893

Add button to toggle whitespace changes

Closes #4271 

**Merge Request**

<img src="/uploads/ea857269faed38a25b63b768d7f3a85b/Screen_Shot_2016-03-23_at_11.32.41_AM.png" width="1157" />


**Diff view**

<img src="/uploads/bc2ac3e4855584f9214c8f3ddf325b06/Screen_Shot_2016-03-23_at_11.32.53_AM.png" width="1211" />

See merge request !3367

Reduce width of parallel diffs

At 50% width the alignment is off on parallel diffs (see https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3785/diffs and view in Side-by-Side)  
Reducing width lines them up:

<img src="/uploads/5775d35b0e86397abd10db6195a8a54d/Screen_Shot_2016-04-22_at_2.19.21_PM.png" width="400px">

Also shifted comment button over to center it properly:  
<img src="/uploads/c2468e15bb65523464a941001c3d7298/Screen_Shot_2016-04-22_at_2.24.33_PM.png" width="200px">

See merge request !3891

Increase screen width breakpoint for hide/show discussion

Closes #15606

See merge request !3915

Allow alternative names for the CHANGELOG file.

"CHANGELOG", "NEWS", "HISTORY", and "CHANGES" are recognized as Changelog files.

Also adds relevant tests for each of these names.

Resolves #14864.

See merge request !3768