Add docs on how to sign json
Spelling
SYN-39: Add documentation explaining how to check a signature
Merge branch 'develop' into server2server_signing
Add section to explain how to sign events such that we can redact message contents
fix grammatics
Read signing keys using methods from syutil. convert keys that are in the wrong format
Add a _matrix/key/v1 resource with the verification keys of the local server
Fix a few pyflakes errors in the server_key_resource
Sign federation transactions
SYN-75 Verify signatures on server to server transactions
Merge branch 'develop' into server2server_signing

Conflicts:
	synapse/storage/__init__.py
	tests/rest/test_presence.py
Merge branch develop into server2server_signing

Conflicts:
	synapse/app/homeserver.py
Merge branch 'develop' into server2server_signing
SYN-75 sign at the request level rather than the transaction level
Verify signatures for server2server requests
Remove debug logging, raise a proper SynapseError if the auth header is missing
Raise a SynapseError if the authorisation header is missing or malformed
Respond with more helpful error messages for unsigned requests
Better response message when signature is missing or unsupported