Implement MQTT as ISAR communication broker

[aeshub]

ISAR currently uses python queues to communicate between the state machine and API implementations. The system should be split in two where the API and the state machine runs in two docker containers. The containers should communicate through an MQTT Broker which runs in a third docker container.

• Any status messages from the state machine will be pushed to the broker and then spread to anyone subscribing to the broker.
• New missions and commands from the API should be supplied through the MQTT broker for the state machine to subscribe to.

[nicholasdalhaug]

We close this issue as it was deemed an overkill and that it makes testing and use more difficult. In a sense replaced by #66