Merge pull request #2658 from matrix-org/rav/store_heirarchy_init

synapse/replication/slave/storage/_base.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/appservice.py

synapse/storage/background_updates.py

synapse/storage/client_ips.py

synapse/storage/deviceinbox.py

synapse/storage/devices.py

synapse/storage/event_federation.py

synapse/storage/event_push_actions.py

synapse/storage/events.py

synapse/storage/receipts.py

synapse/storage/registration.py

synapse/storage/roommember.py

synapse/storage/search.py

synapse/storage/state.py

synapse/storage/transactions.py

tests/storage/test_appservice.py

tests/storage/test_base.py

tests/storage/test_directory.py