Rebuild Conpherence Participants Pane

Summary: Mostly quality of life in renames and moving everything to the view class. Minor CSS tweaks. Fix room handles getting added when adding a new user.

Test Plan: Add to room, remove from room.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16560