Performance improvements

* store @participants in variable
* store result of subscribed? call into variable

In total it reduce amount of SQL queries for issue or merge_request with 10 comments/participants almost twice.

See merge request !883

Add 2FA status to user admin API

This MR adds the `two_factor_enabled` field to the admin's API to indicate whether a given user has enabled 2FA.

See merge request !881

Updated merge request merged web hook to correctly fire action=merged.

I believe this merge request will fix both issues #879 and #498.

If a merge request was merged via the command line, the correct web hook was fired with the field `object_attributes.action = "merge"`. However, if the merge request was merged via the web UI, the webhook would be fired with `object_attributes.action = "open"`.

See merge request !780

Fixes #879
Fixes #498

Explicit error when commit not found in the GitLab CI

!!! SHOULD BE MERGED WITH https://gitlab.com/gitlab-org/gitlab-ci/merge_requests/159

https://dev.gitlab.org/gitlab/gitlab-ci/issues/280

See merge request !871

stop jumping all content on collapsing and expanding the sidebar

When you collapse or expand the sidebar, all content shifts with 5px.

This merge request solves that.

cc @darby

See merge request !1877

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

* store @participants in variable
* store result of subscribed? call into variable

In total it reduce amount of SQL queries for merge_request with 10
comments/participants twice.
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* store @participants in variable
* store result of subscribed? call into variable

In total it reduce amount of SQL queries for issue with 10 comments/participants twice.
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

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

Only look up Commit authors/committers by email

- Removes looking up authors/committers by name
- Renames `User.find_for_commit` to `User.find_by_any_email`

Closes #1850

See merge request !878

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

Closes https://github.com/gitlabhq/gitlabhq/issues/9391

- Removes looking up authors/committers by name
- Renames `User.find_for_commit` to `User.find_by_any_email`

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