Merge branch 'develop' into event_signing

scripts/basic.css

scripts/gendoc.sh

scripts/nature.css

synapse/api/events/factory.py

synapse/federation/pdu_codec.py

synapse/federation/persistence.py

synapse/federation/replication.py

synapse/federation/units.py

synapse/handlers/message.py

synapse/rest/presence.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/transactions.py

tests/federation/test_federation.py

tests/federation/test_pdu_codec.py

tests/handlers/test_federation.py

tests/handlers/test_presence.py

tests/handlers/test_typing.py

tests/test_state.py

webclient/app-filter.js