Fix auto doc group names
Copter: roll and pitch nudging in RTL descent
AC_WPNav: add clear_pilot_desired_acceleration

This allows quickly clearing out the pilot desired acceleration for
loiter contoller.
Copter: RTL always land if in radio failsafe

Resolves issue in which vehicle would get stuck at RTL_ALT_FINAL if
failsafe occured.
Also clear out pilot acceleration from loiter controller if failsafe
occurs during the final descent.
Copter: Loiter clears out pilot acceleration when failsafe occurs

This ensures invalid pilot desired accelerations are cleared from the
loiter controller.  This is probably not strictly necessary because the
vehicle should switch out of Loiter and into RTL during failsafe.
AP_NavEKF: Add ability to inhibit in-flight mag cal and clean up moding

This will enable in-flight magnetometer calibration to be inhibited unconditionally,
This is required for long balloon carriage flights where ground speed can be high
enough to put it into in-air state, but with very poor observability of magnetic field
states causing bad state estimates and heading offsets to develop over time.

The mode control for wind and magnetic field state inhibit has also been explicitly
defined and cleaned up