Added the urdf_string parameter to parseTransmissionsFromURDF().
Added the robot_namespace and urdf_model parameters to initSim().
Added "joint_limits_interface" and "urdf" to the build dependency list.
Additional parameters are passed to robot_hw_sim->initSim(). These parameters
are used by the joint limits interface.
Added "joint_limits_interface" and "urdf" to the component list.
joint_limits_interface is now used to enforce limits on effort-controlled
joints.