Add project.all for API if admin

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
API: projects/all tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
update projects api docs

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
better wording for api doc

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'feature/api_projects_all' of /home/git/repositories/gitlab/gitlabhq