move filter_events_for_client out of base handler

Shuffle when we get the signing_key attribute.

Wait until we sign a message to get the signing key from the homeserver
config. This means that the message handler can be created without
having a signing key in the config which means that separate processes
like the pusher that don't send messages and don't need to sign them can
still access the handlers.

Correctly handle NULL password hashes from the database

Shuffle some methods out of base handler

Send email notifications for missed messages

Implement basic ignore user API

    Remove templates-vector and theme templates with variables instead
    Switch to matrix.to URLs by default for links

Remove templates-vector and theme templates with variables instead
Switch to matrix.to URLs by default for links

Add and use get_domain_from_id

Add some log information at returned replication streams

Add cache to get_user_by_id

Run transaction queue on reactor

Queue events by room for persistence

This ensures that any CPU work that happens doesn't block message
sending.