Application services exclusive flag support

Batched get pdu

Add config option to set the soft fd limit on start

Federation rate limit

Process transactions serially.

Application services event stream support

Since the events received in a transaction are ordered, later events
might depend on earlier events and so we shouldn't blindly process them
in parellel.

Modify _simple_select_list to allow an empty WHERE clause. Use it for get_all_rooms and get_all_users.

Previously you just specified the regex as a string, now it expects a JSON
object with a 'regex' key and an 'exclusive' boolean, as per spec.

This requires the notifier to have knowledge of appservice listeners so it can
do the regex checks on incoming invites to see if the state_key matches. It
isn't enough to just rely on the room listeners and store.get_app_service_rooms
as the room will initially not exist or won't be on the ASes radar due to
having none of its users in the room.