Task #8571: Added comment for functions and fix corner case for messages being received from a previous timed-out rpc call. Also fixes a bug with using queues instead of a bus exchange.

Task #8571: Added option for receiving the full ServiceMessage by the service handler in Service.py and allow the service handler to return a ReplyMessage.

Task #8571: We can't pickle the backtrace and exceptions so only use the backtrace string when applicable. Also ForwardExceptions at the client tries to throw the same exception.