Update the v2 filters to support filtering presence.

Split out the schema preparation and update logic into its own module

SH CAS Required Attribute

Split the sections of EventStreamHandler.get_stream that handle presence

Fix some races in the synapse presence handler caused by not yielding…

Allow optional config params for a required attribute and it's value, if specified any CAS user must have the given attribute and the value must equal

Provide ability to login using CAS