Fallback to internal issue tracker if config is invalid.
Use more descriptive name for config check.
Make clearer use of the check.
Count sidekiq processes using String#scan

It seems there is no easy way to count pattern occurences with
String#match.
Update project api doc.
Merge branch 'issue_tracker' of /home/git/repositories/gitlab/gitlabhq
Merge branch 'project_api_readme' of /home/git/repositories/gitlab/gitlabhq
Merge branch 'fix_sidekiq_process_count' of /home/git/repositories/gitlab/gitlabhq