Small DunGen update - beginning of a styling dialog

This time, it only handles two properties, edge width and background color, with limited options for each. More importantly, it lays down the pattern for restyling at generation of a dungeon level.  I'll flesh that out a bit more, and then add styling of individual nodes and edges, so you'll be able to do things like place direction arrows on stairs and slides, make water edges blue, and mark a special room in red. Anyway, its nice to shake some rust off...