MPU9250 heading is slowly drifting

[seandepagnier]

You can enable the debugging output in calibration_fit.py and run boatimu.py directly. This should give a lot of information indicating why calibration did not work.

The debugging is to the console, but I just now hacked together support to output the log into the ui and to update the sigmapoints as the change rather than only if calibration is found. Hopefully this will make calibration easier in the future.