Use state to calculate get_users_in_room

Add get_users_with_read_receipts_in_room cache

Email unsubscribe links that don't require logging in

Fix error in email notification string formatting

and authed by macaroons that let you delete pushers and nothing else

Rather than storing them as UserID objects.

* Add infrastructure to the presence handler to track sync requests in external processes

* Expire stale entries for dead external processes

* Add an http endpoint for making users as syncing

Add some docstrings and comments.

* Fixes

Split out the auth handler

Refactor SyncHandler

special case m.room.third_party_invite event auth to match invites,

Were it not for that fact that you can't use the base handler in the pusher because it pulls in the world. Comitting while I fix that on a different branch.

Use user_id in email greeting if display name is null

special case m.room.third_party_invite event auth to match invites, otherwise they get out of sync and you get https://github.com/vector-im/vector-web/issues/1208

Ensure we always return boolean in push rules

Cache get_event_reference_hashes

Fix room list spidering

Add secondary_directory_servers option to fetch room list from other servers

Limit number of notifications in an email notification

Otherwise it tries to start the remote public room list updating looping call which breaks.