Implement Accept/Reject in ApplicationTransactions, approximately
Summary: Ref T2222. This mostly makes Accept/Reject work. The big missing piece is that overall revision status does not yet update properly. I need to think about how I want that to work a little bit more.
Test Plan: Accepted and rejected some stuff.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2222
Differential Revision: https://secure.phabricator.com/D8333