Landing in auto with laser

This adds auto-landing capability with lasers. Flight tested with a FX61 with varying altitudes and altitude errors. This log shows a smooth landing with a landing waypoint set 20m too high, due to the laser there is no overshoot.

http://dash.oznet.ch/view/wj7ocUYevMpm73hjpVLq7h#TECS_Outer_Loop_PLOT