Merge branch 'develop' into test-sqlite-memory

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/config/email.py

synapse/config/homeserver.py

synapse/federation/replication.py

synapse/federation/transport.py

synapse/handlers/federation.py

synapse/handlers/login.py

synapse/handlers/register.py

synapse/http/client.py

synapse/rest/login.py

synapse/rest/register.py

synapse/storage/__init__.py

synapse/util/emailutils.py

tests/federation/test_federation.py