Conpherence - remove room vs message distinction as far as users are concerned

Summary:
Ref T8488, T8469, T8485.

This is done in regards to T8488 as far as users are concerned. There's still some classes, and etc. that should be re-named probably. T8469 and T8485 are basically moot now though.

Rather than having "Send Message" exposed, just expose "Create Room". Users get the full form. One change is "title" is now required.

This diff removes the concept of "isRoom" entirely.

Test Plan: Verifed a user with no conpherences had sensible data in both column view and full conpherence view. Created rooms with various policies and things worked well.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: chad, epriestley, Korvin

Maniphest Tasks: T8469, T8485, T8488

Differential Revision: https://secure.phabricator.com/D13351