created new 4dof robot tests, modified gains for 2dof robot experiments in 2-dof-motion.cpp. Added experimental data for 4dof which constraints X and controls it using beta in X and fext in Y. There is also matlab compatible version of 4dof which is to generate some data for visualization in matlab. Added updated/better experiments with 2dof, updated gain values are in the source 2dof-motion.