add harmonic notch tracking mode
call AP_GyroFFT::update_freq_hover() from update_throttle_hover()
move gyrofft configuration and control to AP_Vehicle
move fft logging to fft library
This delegates updates to a bank of NotchFilters located at an rpm frequency and harmonics. Center frequency can be updated dynamically. Notch parameters are configurable, including the number of harmonics to filter on. Updates to the filter parameters are optimized across the notch bank. Convert notch bandwidth and frequency to floats.
allow all filter harmonics to be controlled.
add destructor to harmonic notch.
don't allocate sub-filters for harmonic notch if no harmonics set.
