wumpus-basic

Copperbox revision 2277.

I've made anchors pure values again - though I'll need to update Wumpus-Drawing to validate that this makes sense.

Also, I've made more types instances of the affine classes. One pitfall is that I've had to make Images transformable only if they have scalar units. This was something I got rid of from Wumpus-Core, where it was called the PsPoint type class. In Wumpus-Core it was used as a restriction on almost all the affine instances,  now important objects, e.g. Points and Vectors, are only constrained by the numerical classes and Ord. So its reintroduction as a constraint on Images and "ImageAns" is unfortunate but tolerable in the wider scheme of things.