Also updated example request url

Added changelog item

Allow admins to use restricted visibility levels when creating or
updating projects.

Changed from using cases to set the sort variable, to use a one line if/else statement

Added support for order_by and sort parameters, to sort the projects by the specified values.
Updated projects api documentation including the order_by and sort parameters

Always delete repositories from the filesystem when deleting a project.

Update the project API controller to use `Projects::DestroyService`
instead of calling `Project#destroy` directly.

Also add an optional parameter, `:keep_repo`, that allows a project to
be deleted without deleting the repository, wiki, and satellite from
disk.

This change adds POST /projects/fork/:id to the API for forking
a project into the namespace of the authenticated user, like the
"create fork" link in the GUI does. It also calls the same code.

Failure and permission checks (except for conflict) are already
implemented and handled in ForkService and the API, so the added
code is simple and does not alter anything.

* users (#6878, #3526, #4209): Validation error messages are now exposed through 400 responses, 409 response are sent in case of duplicate email or username
* MRs (#5335): 409 responses are sent in case of duplicate merge request (source/target branches), 422 responses are sent when submiting MR fo/from unrelated forks
* issues
* labels
* projects

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

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

To prevent leaking of users info we reduce amount of user information
retrieved via API for normal users.

What user can get via API:

* if not admin: only id, state, name, username and avatar_url
* if admin: all user information
* about himself: all informaion

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>

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>

Added visibility_level icons to project view (rather than just text).
Added public projects to search results.
Added ability to restrict visibility levels standard users can set.

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

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

Share project with group using API.
You must be a master or owner of project in order to do it.

POST /projects/:id/share

Parameters:
  id (required) - The ID of a project
  group_id (required) - The ID of a group
  group_access (required) - Level of permissions for sharing

Change-Id: I1bdd3608d3b46924b5da3ae282c99f85ee4e0dab