Add (Advanced) Custom Fields to Item List

Summary:
Allow PHP-coded Custom Fields to show things in Lists.

Also add Repository to Revision List and Flags to Maniphest lists.

Closes T15133. Ref T15512, T15750

Test Plan: Look at Repository List and Task lists that have flags.

Reviewers: O1 Blessed Committers, aklapper, valerio.bozzolan

Reviewed By: O1 Blessed Committers, aklapper, valerio.bozzolan

Subscribers: aklapper, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15750, T15512, T15133

Differential Revision: https://we.phorge.it/D25548