FlightTaskOrbit: execute MAVLink orbit command

Latest QGC daily supports sending an orbit command. This commit applies
the correct radius, rotation direction, velocity and center position.
Still missing is a check to have global position available and applying
x,y coordinates and altitude independently.

src/lib/FlightTasks/tasks/FlightTaskOrbit.hpp

@@ -86,7 +86,7 @@ private:
 
 	// TODO: create/use parameters for limits
 	const float _radius_min = 1.f;
-	const float _radius_max = 20.f;
+	const float _radius_max = 100.f;
 	const float _velocity_max = 10.f;
 	const float _acceleration_max = 2.f;
 };