Make the policy control a JS dropdown with icons
Summary: Ref T603. After thinking about this for a bit I can't really come up with anything better than what Facebook does, so I'm going to implement something similar for choosing custom policies. To start with, swap this over to a JS-driven dropdown.
Test Plan: See screenshot.
Reviewers: chad, btrahan
Reviewed By: btrahan
CC: chad, aran
Maniphest Tasks: T603
Differential Revision: https://secure.phabricator.com/D7285