Distance sensors service

[dannystaple]

We need to electrically connect distance sensor (s), then have an MQTT service for their data.
For now build and implement for the simple HC-SR04 like sensor types.

input

• /distancesensor_ctl/start -> start producing sensor data
• /distancesensor_ctl/stop -> stop producing sensor data

output

• /sensors/distance:sensor_number, distance

Definition of ready

• Plan for the distance sensor electrical connections

Definition of done

• PR merged with Electronic CAD Files updated to show where sensors connect
• Distance sensors connected to the Raspberry Pi
• PR merged with simple test of sensors
• PR merged with distance sensor service and test of the service, deployed via PyInfra.