wumpus-basic

Copperbox revision 2091.

I've added some new anchor classes for apex and corners. My thinking has changed somewhat on what will be suitable anchors, I suspect corner anchors might be more useful for block diagrams than cardinal anchors and I'll probably change the Rectangle shape (in Wumpus-Drawing) to have proper radial positions for the cardinal anchors rather than corner positions. As cardinal anchors can usually be computed more efficiently than radial anchors it seems sensible to keep both even though there is redundancy.