currently the simple Plot API attaches methods like plot.image, plot.line etc which adds a graphic to the plot. This is kinda matplotlib inspired but could quickly get polluted (i.e. matlab inspired) . What if we prefix these methods with "add", so it becomes plot.add_image, plot.add_line etc. Because then I could also add add this behavior to the GridPlot API to remove the add_graphic step which is just boilerplate, while keeping the api clean. All add_ methods must add something to the plot or Subplot.

@EricThomson thoughts?