Fill thread list on thread view in Conpherence

Summary:
When we access `/conpherence/view/2/` on the desktop, load the thread on the initial response and ajax in the thread list. Basically, the idea is:

  - When we load the thread list, an individual thread, or the widget panel, we send back the piece the user asked for in the response.
  - On mobile, we stop there: we don't ajax in anything else, and just hide the other parts of the layout.
  - On Desktop, we fill out the other layout components via Ajax.

Ref T2421.

Test Plan: Hit `/conpherence/view/2/`, got a full page.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2421

Differential Revision: https://secure.phabricator.com/D5507