Updates the API documentation of groups with infos to return codes. The function calls
in the groups API have updated documentation and return `400 Bad Request` status code
if a required attribute is missing.

The API documentation of repository is updated and now contains infos to status codes.
Code documentation is also adjusted for `GET /projects/:id/repository/commits` and includes infos to
pagination attributes. Tests are updated.

Merge branch 'state-machine-stage-2' of https://github.com/Undev/gitlabhq into Undev-state-machine-stage-2

Conflicts:
	app/models/merge_request.rb

Show only ≤16 lines of codes in a discussion in a MR (issue #2860).

Since search_autocomplete_source rendered with raw all human input should be sanitized to prevent XSS

System hooks code & logic refactoring

Remove function 'check_issue_1059_shell_profile_error' from check.rake as it is not needed anymore

Fix WebHook and special symbols in credentials

Add title for "Remove from team" button

Add transition on search box

It's kind of cool trend to use animated-expanding search box nowadays.
E.g. see Github.

When using web hook with credentials secured web resource, one needs to
put the credentials in the hook URL.

If the credentials contain special symbols (e.g. @ or #), it should be
URL-quoted (e.g. %40 instead of @).

But when Gitlab is making a request, it should unquote the symbols
before base64-encoding them.

The API Documentation for project snippets got infos to return codes. Tests are added
to check status codes when handling project snippets.