Merge branch 'notifier_unify' into notifier_performance

demo/start.sh

synapse/crypto/keyclient.py

synapse/crypto/keyring.py

synapse/federation/federation_base.py

synapse/federation/federation_server.py

synapse/handlers/_base.py

synapse/handlers/events.py

synapse/handlers/federation.py

synapse/handlers/message.py

synapse/handlers/presence.py

synapse/handlers/profile.py

synapse/handlers/room.py

synapse/handlers/typing.py

synapse/http/client.py

synapse/http/matrixfederationclient.py

synapse/http/server.py

synapse/notifier.py

synapse/rest/media/v1/base_resource.py

synapse/storage/_base.py

synapse/storage/event_federation.py