Plot initial/terminal macrostates in one plot

[michalk8]

One more feature that would be fantastic to add to the plot_macrostates method is a mode which="initial_and_terminal", which shows both initial and terminal states. To tell them apart, the names should be modified in the legend such that they show up as initial: macrostate_1, terminal: macrostate_2 etc. I suggested this above already, what do you think? I think this would be a very useful aggregate plotting mode.