Create GUI map/scenario editor

[tbeddy]

According to this write-up, Elite Command had a GUI editor for editing existing maps and making entirely new ones. A similar editor could build off of #40 (once that's done) and make Zetawar more accessible.

[tbeddy]

I'm not sure if this editor should be part of this repo or should be created as another repo within the Zetawar organization in Github. Thoughts?

[djwhitt]

I'd lean toward putting it in the same repo at first and then spinning it out later if it makes sense.