Fix regression where synapse checked whether push rules were valid

Fix regression where synapse checked whether push rules were valid JSON before the compatibility hack that handled clients sending invalid JSON

Implement logout

Use parse_json_object_from_request to parse JSON out of request bodies

Fix logout on password change

Make select more sensible when dseleting access tokens, rename pusher deletion to match access token deletion and make exception arg optional.

Delete old, unused methods and rename new one to just be `user_delete_access_tokens` with an `except_token_ids` argument doing what it says on the tin.

Make key client send a Host header

Use topological orders for initial sync timeline

Fix cache invalidation so deleting access tokens (which we did when changing password) actually takes effect without HS restart. Reinstate the code to avoid logging out the session that changed the password, removed in 415c2f05

Store appservice ID on register

Update users table in a batched manner

SYN-646 - Register endpoint returns refresh_token

Guest registration still doesn't return refresh_token

Pin pysaml2 version to 3.x

This is due to the fact that `from saml2 import config` fails in version
4.x

Add a parse_json_object function

to deduplicate all the copy+pasted _parse_json functions. Also document
the parse_.* functions.

to deduplicate all the copy+pasted _parse_json functions. Also document
the parse_.* functions.

Fix relative imports so they work in both py3 and py27

Idempotent-ise schema update script