Merge remote-tracking branch 'upstream/master' into feat-dockerfile

.gitignore

CHANGES.rst

CONTRIBUTING.rst

README.rst

docs/admin_api/media_admin_api.md

docs/admin_api/purge_history_api.rst

docs/log_contexts.rst

docs/metrics-howto.rst

docs/workers.rst

scripts/move_remote_media_to_new_store.py

synapse/__init__.py

synapse/api/errors.py

synapse/app/_base.py

synapse/app/appservice.py

synapse/app/client_reader.py

synapse/app/event_creator.py

synapse/app/federation_reader.py

synapse/app/federation_sender.py

synapse/app/frontend_proxy.py

synapse/app/homeserver.py