Plane: use a const reference for home
Copter: use a common home with AHRS
AP_InertialNav: use AHRS home location
Copter: changes set_home_position() to setup_home_position() for Inav
AP_InertialNav: added AP_InertialNav_NavEKF wrapper class
Copter: use AP_InertialNav_NavEKF when available