Added display of interactions based on values of the spin matrix. Thickness of the bond depends on the interaction value: a higher interaction corresponds to a thicker bond. Atoms that are in the spin matrix are highlighted in green. To do: - decide if a negative interaction should be displayed in a different way (e.g., by changing color of the bond) - highlight only certain interactions on a MouseClick event (i.e., when clicking on a specific atom, highlight only the interactions of that specific atom)