Summary:
Ref T7707. Available transforms are currently relatively hard-coded and don't really have any support UI.
Modularize them so we can build some support UI.
This doesn't actually //use// any of the new stuff yet: I want to make a clean cutover once I fix the aspect ratio stuff so I can pick up a cachekey/URI change as a side effect.
Test Plan: {F400524}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: chad, epriestley
Maniphest Tasks: T7707
Differential Revision: https://secure.phabricator.com/D12808
c998e44b5a