wumpus-drawing

Copperbox revision 2619.

I've re-worked the Rectangle shape so it no longer depends on Basic.Geometry.

In some ways this is not a improvement - I expect the new code is a wee bit slower and radial anchors are now found by a sweep which can fail (failure is made total by substituting the center as a fall back anchor); but, the old quadrant code is just too esoteric and needs replacing.