Adds script to plot the usage of bandwidth.

plot_stacked_bandwidth.py

     L.get_texts()[4].set_text("4G SCC 3")
     L.get_texts()[5].set_text("4G SCC 4")
 
-    plt.show()
+    if args.save:
+        plt.savefig("{}-used_bandwidth".format(args.save))
+    else:
+        plt.show()