restore msg_id/msg_type aliases in top level of msg dict...
restore msg_id/msg_type aliases in top level of msg dict
msg_id/type must be stored in the header, as only the header/parent/content are actually sent over the wire. But the msg_id and msg_type should remain as aliases in the top-level msg dict, for logic and 0.11 compatibility.
* docs and tests updated to match.
