Updated the categories of Application Settings Form

Changed the categories and order of the application settings accessible by admin/application_settings

Link to issue: https://dev.gitlab.org/gitlab/gitlabhq/issues/2412
Issue will be closed upon approval of this merge request.

Fixes #2412

See merge request !877

Allow user to remove public email address

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2419

See merge request !880

Create SSH keys document

@job I created the next document for your review, which is "Creating your SSH Keys"

Thanks!

See merge request !1875

added link to GitLab Basics

Added link to GitLab Basics

See merge request !1876

Revert README avatar to original version

In my attempt to rid the world of `gitlab_logo.png`, I didn't realize that http://about.gitlab.com was hosted somewhere else and hence the original link worked fine.

See merge request !876

Split rspec and spinach tests in parallel

For https://dev.gitlab.org/gitlab/gitlabhq/issues/2386

See merge request !874

Fix downloading of patches on public merge requests when user logged out

### What does this MR do?

This MR makes it possible to download a diff patch on a public merge request when a user is logged out.

### Why was this MR needed?

An Error 500 would result when a user attempted to click on the "Email Patches" or "Plain Diff" button:

```
NoMethodError - undefined method `id' for nil:NilClass:
  lib/gitlab/backend/shell_env.rb:9:in `set_env'
  lib/gitlab/satellite/action.rb:20:in `in_locked_and_timed_satellite'
  lib/gitlab/satellite/merge_action.rb:49:in `diff_in_satellite'
  app/models/merge_request.rb:219:in `to_diff'
  app/controllers/projects/merge_requests_controller.rb:42:in `block (2 levels) in show'
```

### What are the relevant issue numbers?

* Closes #1225
* Closes #1854 (dup)
* Closes #1858 (dup)

See merge request !872

Admin can see, edit and remove user identities

Related to #1415 and https://dev.gitlab.org/gitlab/gitlabhq/issues/2224Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !843

Fix error when deleting a user who has projects

### What does this MR do?

This MR fixes an error that prevented users from being deleted in the Admin page if the user had personal projects.

### Why was this MR needed?

Deleting a user who had projects would result in an error such as this:

```
Started DELETE "/admin/users/tdb1" for MYIP at 2015-06-22 20:53:02 +0100
Processing by Admin::UsersController#destroy as HTML
Parameters: {"authenticity_token"=>"[FILTERED]", "id"=>"tdb1"}
Completed 500 Internal Server Error in 30ms (ActiveRecord: 6.7ms)

NameError (undefined local variable or method `current_user' for #<DeleteUserService:0x0000000cd01d38>):
app/services/delete_user_service.rb:10:in `block in execute'
app/services/delete_user_service.rb:7:in `execute'
app/controllers/admin/users_controller.rb:89:in `destroy'
```

### What are the relevant issue numbers?

* Closes #1856
* Closes https://github.com/gitlabhq/gitlabhq/issues/9394

See merge request !868

Closes #1225
Closes #1854
Closes #1858

Fixed invalid timestamps in RSS feed #1771

Fixed invalid timestamps in RSS feed by using rfc3339 #1771

See merge request !870

Closes #1856
Closes https://github.com/gitlabhq/gitlabhq/issues/9394

Enable rubocop for tests too

cc @DouweM @rspeicher
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !862

Validate presence of provider field in Identity
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !869

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Animation of Sidebar (video in here)

Edited the CSS of header and sidebar; added a new div of gitlab-logo-container to the html to make things easier.

The transition-duration is set to 0.3s and when the nav bar expands, it opens up over the text, essentially revealing hidden text.

[animation-sidebar-2.mov](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b15996a256d6bed03a19c68549d116e4/animation-sidebar-2.mov)

/cc @JobV @nicolas2

See merge request !849

Allow Admin to filter users by 2FA status

> ![Screen_Shot_2015-06-19_at_4.38.12_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/deba7f2a6b8d1548c1d1ac401e0e35a1/Screen_Shot_2015-06-19_at_4.38.12_PM.png)

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2414

See merge request !852

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Conflicts:
	spec/features/issues_spec.rb
	spec/models/forked_project_link_spec.rb
	spec/models/hooks/service_hook_spec.rb
	spec/models/hooks/web_hook_spec.rb
	spec/models/project_services/hipchat_service_spec.rb
	spec/requests/api/project_members_spec.rb
	spec/requests/api/projects_spec.rb
	spec/requests/api/system_hooks_spec.rb
	spec/services/archive_repository_service_spec.rb
	spec/support/matchers.rb
	spec/tasks/gitlab/backup_rake_spec.rb

Fix avatar tests to use banana_sample.gif

Fixes tests that were broken in f5e0e5c0 due to the purge of `gitlab_logo.png`.

See merge request !866

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>