Remove the email patches link for merge commits

Rugged's `to_mbox` method doesn't work for merge commits, so don't display the option to download them as email patches.  This is part of the fix for #1878, and gitlab/gitlab_git!27 allows a plain diff to be generated for a merge commit.  Together these changes should prevent the 500 errors described in the issue.

cc @sytse

See merge request !1737

We've moved external trackers to service, remove from gitlab.yml.

Fixes #1937

See merge request !1743

Improve UI for issues filters

![filters-ui](https://gitlab.com/gitlab-org/gitlab-ce/uploads/31109bb069a5f42a9b83c2fb44af288b/filters-ui.png)

See merge request !472

Prevent holding Control-Enter or Command-Enter from posting comment multiple times.

See private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2184

See merge request !467

Fix typo 'projecti' to 'project' in ssh doc [ci skip]

There was a typo in the SSH doc: projecti was written instead of project.

See merge request !461

Big refactoring of issues filters

* No magic numbers for issues filtering
* Squash project users selectbox and users selectbox into one class
* Move from API autocomplete to GitLab internal one
* Smarter filter for project/group/all issues
* Use selectbox with searchbox for assignee/author/milestone/label
* Switch to ajax filter for issue author/assignee

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/1035

See merge request !466

* Squash project users selectbox and users selectbox into one class
* Move from API autocomplete to GitLab internal one
* Smarter filter for project/group/all issues
* Use selectbox with searchbox for assignee/author/milestone/label
* Switch to ajax filter for issue author/assignee

Separate Dockerfile for Data and Application

This is based on #1158

Instead of creating data container from same docker image, we create separate docker image for data container to avoid keeping original docker image after upgrading to new version. (That results in 1GB space that cannot be freed)

See merge request !409

Set Application controller default URL options to ensure all url_for calls are consistent

### What does this MR do?

This MR sets the app controller's `default_url_options` so that all `url_for` calls are consistent.

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

Setting these options may simplify `url_for` calls that load the GitLab options already. I did not want to touch existing code yet. I'm also not sure if there are other options that need to be included.

### Why was this MR needed?

If you run GitLab behind a reverse proxy or in a Docker container, you don't want a user to be seeing the local IP and port on which GitLab is running (e.g. 192.168.1.1:8080). Right now there are places where this internal data is leaked (e.g. see the URL in Profile Settings -> Account -> Username; this uses `user_url`).

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

#1249

See merge request !453

Fix EmailsOnPush.

See private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2185.

See merge request !459

Add archived status to Admin > Project page

Renamed Buildbox to Buildkite.

Change directory when removing old backups

Fixes errors when deleting old backups in the `gitlab:backup:create` rake task.  See #2177.

See merge request !1740

Capitalize js class name

See merge request !457

Fix broken side-by-side diff view on merge request page

### What does this MR do?

This MR fixes the side-by-side diff that was broken in v7.9.0. The "Inline" and "Side-by-Side" buttons are now always rendered with HTML links instead of changing depending on whether the code diff was requested in JSON format.

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

Is there a better way to fix this? The links in JSON format may be desirable if there were a JavaScript hook to handle the buttons, but as far as I can tell there isn't at the moment.

### Why was this MR needed?

The issue is that the code diffs can be generated either by the JavaScript handler or the regular HTML. With the forcing of JSON request format in 27e75344, the JavaScript handler requests the page in JSON format, which it then uses to render the page. However, this has the unintended side effect of requesting that the "Inline" and "Side-by-Side" buttons have references to a JSON-formatted link.

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

#1294

See merge request !460

UI improvements

* Fix diff header for discussion
* Remove unused doorkeeper layout
* Nicer well
* Replace alerts with well where alert is not needed

See merge request !458

Closes #1294