Implement restricted namespace checks. Begin fleshing out the main hook for notifying application services.

Expose handler.get_services_for_event which manages the checks for all
services.

Conflicts:
	synapse/handlers/__init__.py
	synapse/storage/__init__.py

Rejections

Client v2 sync

Add doc string for __nonzero__ overrides for sync results, raise not implemented if the client attempts to do a gapless sync

Conflicts:
	synapse/storage/schema/im.sql

Replication split

Means that now you can't do exact matches even in override rules,
but I think we can live with that. Advantage is that you'll now
always get back what was put in to the API.

Rejections storage

Conflicts:
	synapse/storage/__init__.py

Client v2 filter