Yacht Devices modules

The Python Gateway has four custom modules: ydpg with functions specific to the Python Gateway, nmea0183 and nmea2000 to handle NMEA data, and ydsolve (it provides a simple least squares solver and can be used to calibrate external sensors, such as fuel tank sensors). By default these modules, except ydsolve, are imported in boot.py and you don’t need to do it in main.py.