R1:1f2cf78c1b54

Display committed date in Revision Status field

Summary:
This is slightly more complicated for this reason:

- We don't set `dateCommitted` for normal commits, only for markcommitted.
-- We need to add this date to old revisions now.

Test Plan:
Reparse a revision - commit date was set.
Conduit `markcommitted` - commit date was set.
Run SQL script.
Display closed revision.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2282