Merge remote-tracking branch 'origin/develop' into markjh/worker_config

CHANGES.rst

jenkins-dendron-postgres.sh

synapse/__init__.py

synapse/federation/federation_base.py

synapse/federation/federation_client.py

synapse/federation/federation_server.py

synapse/federation/replication.py

synapse/handlers/auth.py

synapse/handlers/federation.py

synapse/http/client.py

synapse/rest/media/v1/preview_url_resource.py

synapse/types.py