Merge remote-tracking branch 'origin/develop' into webclient_data_centralisation

CHANGES.rst

UPGRADE.rst

cmdclient/console.py

docs/client-server/swagger_matrix/api-docs-registration

docs/specification.rst

synapse/api/constants.py

synapse/api/events/__init__.py

synapse/api/events/factory.py

synapse/federation/replication.py

synapse/federation/transport.py

synapse/handlers/events.py

synapse/handlers/federation.py

synapse/handlers/message.py

synapse/handlers/register.py

synapse/handlers/room.py

synapse/http/client.py

synapse/rest/events.py

synapse/rest/register.py

synapse/rest/room.py

synapse/server.py