Use new invalidate_many cache invalidation to invalidate the event_push_actions cache appropriately.

Only fetch events for rooms and receipts

Reduce number of calls to get_unread_event_push_actions_by_room

This reverts commit d7265977.

SYN-606: Peeking does not wake up /events

Cache dns lookups, and use the cache if we fail to lookup servers later

If a real user attempted to first peek into one room, and then another,
their room event stream would not be woken up for events in the later
room.

Remove member event rule as per SYN-607

Push badge counts

Don't explode when given a unicode username in /register/

Whine if we give a from param to /sync

Allow non-guests to peek on rooms using /events

Add storage function to get all receipts for a user. Also add some cache invalidation to the receipts storage because there wasn't any, and remove a method that was unused.