Matrix plots

If PLOT_MATRICES=True, plots of the adjustable elements of four matrices at each iteration are created: the gradient estimates, stationary distributions, matrices in the unconstrained space and the transition matrices. If SAVE_OUTPUT=True, the plots are saved as pdf files with name CURRENT_INSTANCE_NAME_PLOT_TYPE, where PLOT_TYPE is equal to gradient, stat_dist, theta and transition, respectively, in a folder named according to INSTANCE_OUTPUT_DIRECTORY. These plots are only available if ALGORITHM_RUN_TYPE="single".