Optimizing My Gcode Generators

I had originally written several programs intended to produce gCode for the different sides of this part: bottom, sides, slot, and I was going to have to write a top program as well, and I suddenly realized that rezeroing the axes was not that big a task, and bottom, top, and sides were really the same program, excavate a rectangle with different depths and widths, so I have replaced bottom, top, and sides with excavate, and  different command line arguments.  This is not only simpler for this part, but makes it easy to produce other parts in the future.