Added willEditTask and didEditTask for Differential.
Summary: Added constants to PhabricatorEventType. Modified DifferentialRevisionEditor and DifferentialCommentEditor.
Test Plan:
Created a revision. Edited and made a comment on that revision. It's updating as usual. I think nothing broke may be it's working.
Let me know if I have done it correclty.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin, AnhNhan
Maniphest Tasks: T2899
Differential Revision: https://secure.phabricator.com/D5869