Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15577

Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

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

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

The good:

 - You can do a merge request for a forked commit and it will merge properly (i.e. it does work).
 - Push events take into account merge requests on forked projects
 - Tests around merge_actions now present, spinach, and other rspec tests
 - Satellites now clean themselves up rather then recreate

The questionable:

 - Events only know about target projects
 - Project's merge requests only hold on to MR's where they are the target
 - All operations performed in the satellite

The bad:

  -  Duplication between project's repositories and satellites (e.g. commits_between)

(for reference: http://feedback.gitlab.com/forums/176466-general/suggestions/3456722-merge-requests-between-projects-repos)

Fixes:

Make test repos/satellites only create when needed
-Spinach/Rspec now only initialize test directory, and setup stubs (things that are relatively cheap)
-project_with_code, source_project_with_code, and target_project_with_code now create/destroy their repos individually
-fixed remote removal
-How to merge renders properly
-Update emails to show project/branches
-Edit MR doesn't set target branch
-Fix some failures on editing/creating merge requests, added a test
-Added back a test around merge request observer
-Clean up project_transfer_spec, Remove duplicate enable/disable observers
-Ensure satellite lock files are cleaned up, Attempted to add some testing around these as well
-Signifant speed ups for tests
-Update formatting ordering in notes_on_merge_requests
-Remove wiki schema update
Fixes for search/search results
-Search results was using by_project for a list of projects, updated this to use in_projects
-updated search results to reference the correct (target) project
-udpated search results to print both sides of the merge request

Change-Id: I19407990a0950945cc95d62089cbcc6262dab1a8

The notes API documentation updated with return codes. API now returns `400 Bad Request` if
required attributes are not present. Return codes are documented now, also tested in added tests.
The documentation now reflects the current state of the API.

If a note is created with a POST request via API (`/projects/:id/notes`) status
code 400 is returned instead of 404. The resource itself exists but the request
is incomplete. Specs added to check different status codes when accessing, creating
and updating notes.