Adding Ik used for joint impedacne control

[zhuyifengzju]

• Inverse kinematics based on mujoco computation
• An example of running inverse kinematics and send the computed joint trajectories using joint impedance control. The example also automatically read the current joint state so that the trajectory will be computed based on the current robot state.
• Before execution, the mujoco visualizer is automatically turned on, where the joint sequence will be visualized. We highly recommend you to turn on this feature during debugging face. Any consequence of running invalid joint sequence will be your own responsibility.