GUI Framework in place

We're ready to begin linking the model and the view together. Finishing
the GUI requires another few hours; creating a new frame when the Add
Factory button is pressed, finishing touches on component placements,
creating final versions of the sector and sector linking images, and
generating the text for the lower panel. The relative production bars,
resource flow arrows, and selected-sector highlighting will be left for
later, until the model and view are somewhat connected.