Storage for pdu signatures
Begin implementing state groups.
Add missing package storate.state
Merge branch 'develop' into event_signing
Begin making auth use event.old_state_events
persist hashes and origin signatures for PDUs
Sign outgoing PDUs.
Start implementing the invite/join dance. Continue moving auth to use event.state_events
Include hashes of previous pdus when referencing them
Hash the same content covered by the signature when referencing previous PDUs rather than reusing the PDU content hashes
Finish implementing the new join dance.
move 'age' into 'meta' subdict so that it is clearer that it is not part of the signed data
Rename 'meta' to 'unsigned'
Merge branch 'develop' into event_signing

Conflicts:
	synapse/federation/replication.py
Use state groups to get current state. Make join dance actually work.
Fix bug where people could join private rooms
Remove signatures from pdu when computing hashes to use for prev pdus, make sure is_state is a boolean.
It doesn't want a dict
Add script to hash exisitng history
Merge branch 'develop' of github.com:matrix-org/synapse into federation_authorization

Conflicts:
	synapse/federation/transport.py
	synapse/handlers/message.py