gitlab-ce, workhorse: pass new fields in Repository message
Depends on #145 (closed) (shard field in proto).
Even if the gitaly server still ignores the storage_name and relative_path fields we can already do the work of making sure they are passed on reach RPC. This also means passing them down to workhorse from gitlab-ce, and sending them out from workhorse on each RPC.
The point of this is to prepare the way for the final change where gitlab-ce starts using storage_name+relative_path.