wumpus-basic

Copperbox revision 1771.

I've replaced FreeLabel with a new element Plaintext. Plaintext isn't a Shape as it doesn't generate a path, but it does have some Shape-like properties - it can be rotated and translated, and it generates anchor points.

The down side to these changes to Shape and the introduction of the new Plaintext type is that labelling shapes is now more complicated, I'll have to look into a plumbing function to see if I can make Shapes and Plaintext labels in the same expression.Also, at some point Plaintext should be extended to handle multi-line text.