[Firmware] Implement basic bmi160 support

[TheButlah]

116 added a basic imu implementation which reads the gyro velocity from the bmi. However, we should be using rotational position rather than velocity, so we need to integrate or use sensor fusion.

Also, we need to test that the math of the conversion on velocity and to euler angles actually made sense.

[TheButlah]

176 and #173 added the first fusion algorithm, DCM. But It doesn't seem to be working. Most likely the axes need to be reordered.

[TheButlah]

It looks like this is actually working properly after all.