Notify on e2e events

Handle fact that _generate_room_entry may not return a room entry

Fix and clean up publicRooms pagination

Make public room search case insensitive

Add very basic filter API to /publicRooms

Change get_pos_of_last_change to return upper bound

Enable state caches on workers

Use stream_change cache to make get_forward_extremeties_for_room cache more effective

Add cache to get_forward_extremeties_for_room