Clean code of 2dof simulations

...t_2dof/launch/simple_robot_rviz_simulation_2dof_launch.py

..._2dof/simple_robot_2dof/forward_kinematics_node_2dof_1.py

..._2dof/simple_robot_2dof/forward_kinematics_node_2dof_2.py

...imple_robot_2dof/simple_robot_2dof/reference_node_2dof.py

ros2_ws/src/simple_robot_2dof/urdf/simple_robot.urdf