Extend yml syntax for only and except to support specifying repository path

This allows to limit execution of jobs to specific repository.

For example:
```yaml
job:
  only:
    - branches@gitlab-org/gitlab-ce
  except:
    - master@gitlab-org/gitlab-ce
```

The above will run `job` for all branches on `gitlab-org/gitlab-ce`, except master.

@dzaporozhets @JobV @vsizov Please review.


See merge request !1720