hector_quadrotor_gazebo_plugins: added wrench publisher to the
quadrotor_simple_controller plugin
Merge remote-tracking branch 'origin/groovy-devel' into hydro-devel

Conflicts:
	hector_quadrotor_gazebo_plugins/src/gazebo_quadrotor_simple_controller.cpp
hector_quadrotor_model: added try..catch block to catch runtime error if
the gazebo time is very small