Summary: Ref T2217. Cleans up the table names. Moves old data to `maniphest_transaction_legacy`. We'll drop that eventually once it's more clear that I didn't break the world.
Test Plan: Did reads/writes to/from these tables.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2217
Differential Revision: https://secure.phabricator.com/D7094
