Merge pull request #2252 from matrix-org/erikj/user_dir

synapse/handlers/user_directory.py

synapse/notifier.py

synapse/rest/__init__.py

synapse/rest/client/v2_alpha/user_directory.py

synapse/server.py

synapse/state.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/events.py

synapse/storage/schema/delta/42/user_dir.py

synapse/storage/user_directory.py

synapse/types.py

synapse/util/caches/stream_change_cache.py