Load all diff properties in revision view

Summary:
We need to load all properties with some prefix in one field.
We can't merge them in one property because there will be a race condition for update (we don't have API for load+update+save).

Instead of providing API for this and complicating the code even more, just load everything unconditionally.
It shouldn't waste much bandwith or memory because we use most of the properties anyway.
It also looked overengineered to me.

Test Plan: Displayed revision with fields using diff properties.

Reviewers: epriestley, royw

Reviewed By: royw

CC: aran, royw, Korvin

Differential Revision: https://secure.phabricator.com/D3676