Spaces + Diffusion - make creating a new repository work again
Summary: Fixes T8702. Needed to teach these controls how to serialize / unserialize themselves in that they are storing two values (policy phid + space phid) nowadays
Test Plan: made a new repo successfully with policy as described in T8702. Also edited policy successfully.
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Maniphest Tasks: T8702
Differential Revision: https://secure.phabricator.com/D13472