hector_quadrotor_gazebo: reduced gaussian noise stddev for barometric pressure from 0.5 to 0.1

Conflicts:

	hector_quadrotor_gazebo/urdf/quadrotor_sensors.urdf.xacro
hector_quadrotor_controller: fixed time step calculation in propulsion model plugin
hector_quadrotor_urdf: fixed sonar height sensor field_of_view (degrees to radians)