hector_quadrotor_model: use precompiled codegen libraries if available
hector_quadrotor_gazebo: a few fixes for RTT integration in hector_quadrotor. Added urdf macro for rtt_gazebo_plugin macro.

Conflicts:

	hector_quadrotor_gazebo/urdf/CMakeLists.txt
	hector_quadrotor_gazebo/urdf/quadrotor_plugins.gazebo.xacro.in
	hector_quadrotor_gazebo/urdf/quadrotor_rtt_controller.gazebo.xacro