Simple refactor, moving helper into its own package.
Basic PlotModel. I'm sure this will grow later, but for now, it addresses the basic needs: Who owns it, where is it, and who can work on it.
XZ, not XY.
Plot actually, as of right now, doesn't need to know its XZ location -- handled via ID by controller.
Basic Plot management stuff. Commands are not handled, yet.
Some event handlers to go with the plot system.
Should really look into removing the default comment from IDE...