Convert remaining Pholio image transactions to modular transaction framework

Summary: Also cleans up now-dead code relating to old transactions

Test Plan: Created lots of mocks, replaced their images, added/removed images, changed the sequence, verified expected DB xaction rows, Mock updates, and correct rendering of timeline.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D17892