Add a .gitreview to allow us to use git-review

This allows us to use 'git review' to push the local changes to review.
Also, it's possible to use 'git review -d XXXX' to download a changeset
locally for testing, where XXXX is the tag for the change on gerrit.

This was pushed for review using 'git review' :)

Change-Id: I0ede8f18130b9c3fa42989d54e31597bbf932d18