Mostly directory structure and convenience refactoring.
Implemented Publisher and Subscriber abstract base class for the sake of type hints.
Moved mqtt, zmq and serial wrappers to msb/networking to not clutter msb/ too much
Added get_publisher and get_subscriber factory functions. Use with
zmq_pub = get_publisher("zmq")
mqtt_sub = get_subscriber("mqtt", "/sensor/temp")```
4. msb/mqtt and msb/zmq have NOT been deleted but are considered deprecated.
5. Added serial pub/sub draft
6. Added msb/network/packer which provides a common interface for serializing and deserializing. Not fully tested.
7. Started work on unittests with Mock objects.
Mostly directory structure and convenience refactoring.