Swap transactions and initialization over to modern status constants

Summary: Ref T2543. Update these for the modern stuff.

Test Plan: Created a new revision, got a revision in the right state ("Needs Review"). Accepted, planned, requested, abandoned revision; state transitions looked good.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18415