Conpherence - sort participant list in main conpherence with an actual algorithm

Summary: Fixes T7765. The existing sort was based on when people were added to the conpherence and basically feels random in time. Instead, sort current logged in user to the top and make the rest of the list alphabetical.

Test Plan:
viewed a conpherenece and noted my logged in user at top and the rest was sorted alphabetically
viewed a room that i was not a participant in and participant list rendered correctly

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7765

Differential Revision: https://secure.phabricator.com/D12302