Remove gyro drift fix-up

The orientation sample is a better demo of the differences between the
three rotation sources if the gyro drift fix-up is removed.
Compass sample now uses Kalman filter

This commit updates the compass sample to use a Kalman filter instead
of moving average.
Remove obtuse quaternion interpolation

When I calculate the quaternion to represent the accelerometer /
magnetometer rotation, it could end up using an inverted axis from
the gyro based quaternion.  This would cause the Kalman filter to
slowly correct by performing a ~360 degree rotation.  I now flip the
sign of the accel/mag quaternion if the angle between it and the
predicted quaternion are obtuse.