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

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>

These fixes were performed automatically by Rubocop's `-a` flag.

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>

Conflicts:
	app/views/admin/users/show.html.haml

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

Also MySQL complains when you change a field to be not null if any
existing records already have a null value, so this updates those rows.