Conpherence - get lots of rooms stuff hooked up nicely

Summary:
Ref T7566. This does a big chunk of what's left

• Main view
  • "Rooms" sub header
    • 5 Rooms shown at a time, with room you're looking at in the top on page load
      • e.g. viewing /conpherence/x/ the room x is at top always
      • solves corner case of when you have yet to "join" the room
    • "See More" link takes you to application search for rooms you have participated in
    • if no rooms, there is a "Create Room" and "Find Rooms" links.
  • "Messages" sub header
    • same as before
  • policy icons showing up in the menu
• Durable column view - still just the latest N, no changes really there
• Transactions - special cased rendering to try to say room vs thread as appropos
• Bug fix - we weren't recording the initial participants transaction post D12177 / D12163. This fixes that.

Should probably test pagination, and if you want to show more than 5 rooms of have it behave more like messages (where you can wind up in the middle of a paginated list) that will be more work. Also, if lots of messages / rooms (100 is the limit) we might not display rooms if we're supposed to. Yay whale usage! :D

Test Plan: made a new room - success. made a new message - success. viewed a room from /conpherenece/room/ i wasn't a participant in and noted it showed up at the top of the five rooms. clicked around rooms and stuff loaded nicely.

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7566

Differential Revision: https://secure.phabricator.com/D12178