Wumpus

Copperbox revision 855.

I've added graphics state changes to the label and path constructors of the Picture type, so now pictures can be coloured, have changes of line width etc. That said, I'm sure what a reasonable way of setting these attributes is going to be. Currently there is a simple prototype hack to change font properties but that isn't very good. As the picture type is really a tree, maybe I'll have to use downwards inheritance as per attribute grammars.