Conpherence - allow for public rooms to really work

Summary: Fixes T8102. This makes public rooms actually work. Also lets users see the search listings page so they can wander into all public rooms without logging in.

Test Plan: As logged out user, visited ZXX and ZYY. ZXX was public, so I could see it and had a little "Login to Participate" button in the bottom. ZYY was not public so I was prompted to login. Back on ZXX I clicked the Conpherence crumb and got a sensible UI where most links prompted me to login. CLicked "search" and saw listings for all public rooms.

Reviewers: epriestley, chad

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8102

Differential Revision: https://secure.phabricator.com/D12778