Perform derived index updates in TransactionEditor

Summary: Ref T2222. We have two tables (one for hashes; one for paths) which were unevenly updated before. Now, update them consistently in the TransactionEditor.

Test Plan: Created a revision, saw it populate this information.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8455