hector_quadrotor_controller: added installation rule for launch and params directories
hector_quadrotor_controller/hector_quadrotor_gazebo: disabled propulsion model

The current version produces thrust even with zero motor voltages...
hector_quadrotor_teleop: added slow button (btn 6 on Logitech Gamepad)
hector_quadrotor_demo: updated demo launch files
Merge branch 'hydro-devel' into ros_control