SW-699: raise in BusListener when it is detected that the provided handler is an empty template handler

SW-699: added UsingToBusMixin, and (re)use that in all the ServiceMessageHandlers and some AbstractMessageHandler derivatives

SW-699: do not use direct_address anymore. only send messages to the exchange with a proper routing_key

SW-699: fixed doctest. added check for ack/reject lofar message. reuse current queue connection when getting nr_of_messages_in_queue.

SW-699: added documentation to RPCClientContextManagerMixin. renamed rpc_service.py module tp rpc.py, and it's classes to RPCClient and RPCService. Moved Request and ReplyMessage into rpc.py module. Mader MessageFactory and used it in FromBus and rpc.py

SW-699: refactored/simplified RPC as well. Refactored has_args/has_kwargs quirks in RequestMessage. Have one simple API.

SW-699: major refactoring of the messagebus's BusListener and Service. Together with Jan-David and Auke, I decided to only allow a single API for the service, and we chose the most commenly used API based on the MessageHandlerInterface which we refactored into the ServiceMessageHandler. TODO: add docstrings, fix tests, adapt all Services in lofar python code.

SW-699: fixed some typos. Made TemporaryQueue bindable to and exchange. Route RPC-ReplyMessages via exchange to temporary reply queue

SW-699: major rewrite of FromBus/ToBus, AbstractBusListener and RPC/Service based on kombu/rabbitmq. This allows us to use a single lofar exchange (multiple exchanges are still allowed), and using auto-generated designated queues with subject based routin_keys.

SW-699: Make notifications unconfigurable, greatly reducing complexity of the higher abstraction layers.