Provide revision status information via API all "differential.revision.search"

Summary: Ref T2543. Now that the integer status constants are banished to the internals, we can expose status information from "differential.revision.search".

Test Plan:
Searched for revisions.

{F5093873}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18400