Copter: reset battery_fs after dis/rearming
Copter: define limit for baro vs inav alt disparity
Copter: typo fix for baro vs inav alt disparity definition
AC_WPNav: add loiter_soften_for_landing method

This resets the position target to the current location.
Copter: soften loiter target when maybe landed

Applies to auto's land, land, loiter, pos hold and rtl flight modes
Copter: add land_complete_maybe flag
Copter: rename land_maybe_complete function