Merge branch 'client_v2_filter' into client_v2_sync

synapse/api/filtering.py

synapse/rest/client/v1/push_rule.py

synapse/rest/client/v1/pusher.py

synapse/rest/client/v2_alpha/__init__.py

synapse/rest/client/v2_alpha/filter.py

synapse/server.py

synapse/storage/__init__.py

synapse/storage/filtering.py

synapse/storage/push_rule.py

synapse/storage/schema/delta/v13.sql

synapse/storage/schema/filtering.sql

synapse/storage/stream.py

tests/api/test_filtering.py

tests/rest/client/v2_alpha/__init__.py

tests/rest/client/v2_alpha/test_filter.py