Clean code of 3dof simulation

...t_3dof/launch/simple_robot_rviz_simulation_3dof_launch.py

..._3dof/simple_robot_3dof/forward_kinematics_node_3dof_1.py

..._3dof/simple_robot_3dof/forward_kinematics_node_3dof_2.py

...imple_robot_3dof/simple_robot_3dof/reference_node_3dof.py

ros2_ws/src/simple_robot_3dof/urdf/simple_robot.urdf