Rename "transactionpro" table to "transaction"

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