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

New state resolution

Conflicts:
	synapse/storage/__init__.py
	synapse/storage/schema/delta/v12.sql

Change 'from' in notification pokes to 'sender' to match client API v2. Send sender display names where they exist.

Add default push rules including setting a sound for messages mentioning your username / display name

split the storage and management of filters from the actual filter code
and don't have to load a filter from the db each time we filter an event