autotest: removed obsolete navigation parameters for ArduPlane
AP_GPS: fixed initialisation error in uBlox driver

found with valgrind
AP_InertialSensor: ensure parent class is initialised in instance classes
Plane: removed HIL_MODE_ATTITUDE 

we really need full sensors for HIL with the L1 controller. The flight
is also _much_ better with sensors HIL.
Plane: added LEVEL_ROLL_LIMIT parameter

this replaces both TKOFF_HEAD_HOLD and RUDDER_STEER, allowing users to
instead select a roll limit for takeoff and landing
Plane: update author list
AC_WPNav: first implementation
AC_WPNav: add distance and bearing to target methods
Copter: integrate AC_WPNav
AC_WPNav:  bug fix to dt calculation
Copter: replace set_next_WP with direct call to wp_nav
AC_WPNav: add get_target_alt

Required because waypoint controller will be modified to control
altitude
Copter: add panorama to CIRCLE mode

Yaw will slowly rotate if CIRCLE_RADIUS is set to zero
Circle center is projected forward CIRCLE_RADIUS from current position
and heading
AC_WPNav: added set_target_alt
Copter: removed next_WP

Use the wp_nav.get_target_alt or controller_desired_alt in it's place
AC_WPNav: replace get_target_alt with get_destination_alt
Copter: replace wp_nav.get_target_alt with get_destination_alt
Copter: remove remnants of fast_corner
InertialNav: add get_velocity method
AC_WPNav: add set_loiter_target to use velocity

Target can be set in front of the copter to reduce the bounce back to
the position where loiter was engaged.