Update the v2 sync API to work as specified in the current spec.

Remove unused room_id arg

Bounce all deferreds through the reactor to make debugging easier.

If all deferreds wait a reactor tick before resolving then there is
always a chance to add an errback to the deferred so that stacktraces
get reported, rather than being discarded.

Update the v2 filters to support filtering presence.

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

Apply the filter the 'timeline' and 'ephemeral' keys of rooms.
Apply the filter to the 'presence' key of a sync response.

SH CAS Required Attribute

Split the sections of EventStreamHandler.get_stream that handle presence