fixed the problem that joint_id=6 only makes sense for ur5e. now i use...

fixed the problem that joint_id=6 only makes sense for ur5e. now i use ee_frame_id = pin.getFrameId('tool0') which gets the (correct) ee frame regardless of the robot. this requires pin.updateFramePlacement, but this can be done for only one frame so who cares. having this said, i have to test all other functions to see if this makes sense or not