Wumpus

Copperbox revision 893.

I've tidied up the path construction code in Core.Picture by adding two type classes PicPath and MultiPath that wrap up path attributes. I haven't done this for labels yet, as I'm wondering whether or not the current label type needs improving first.

The PicPath and MultiPath classes were inspired by the Node class in Iavor S. Diatchki's nice XML.Light library.