Conpherence - more threadManager stuff and get scrolling working

Summary: Ref T7014. The main conpherence view is kind of broken without this in subtle ways because of /conpherence/ versus /conpherence/x/ init'ing things differently; this fixes that. Moves more normal view conpherence logic into threadManager. Makes all the display code happen outside of threadManager, setting us up for some display manager later maybe.

Test Plan: sent messages, updated title, etc and the messages pane auto scrolled correctly!

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7014

Differential Revision: https://secure.phabricator.com/D12035