Implement more Differential fields on ApplicationTransaction/CustomField
Summary:
Ref T2222. Ref T3886. Gets the storage-based fields working.
This requires future changes to actually do anything, all this code is inactive.
Test Plan: {F118863}
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3886, T2222
Differential Revision: https://secure.phabricator.com/D8357