- remove class _mag_sample_delayed
- update mag fusion call graph to use mag sample delayed functionally
- Ekf::resetMagHeading()
- use low pass mag directly, but check if valid (magnitude)
- MAG_FUSE_TYPE_INDOOR treat like auto if heading required
- introduces new parameter EKF2_PREDICT_US to configure the filter
update period in microseconds
- actual filter update period will be an integer multiple of IMU