Revision 1535

* Thuban/Model/data.py (SHAPETYPE_POLYGON, SHAPETYPE_ARC)
(SHAPETYPE_POINT, Shape): Move these constants and classes from
layer.py to data.py
(ShapefileStore.__init__): More Initialization for the new methods
and functionality.
(ShapefileStore.ShapeType, ShapefileStore.NumShapes)
(ShapefileStore.BoundingBox, ShapefileStore.ShapesInRegion)
(ShapefileStore.Shape): New methods that were formerly implemented
in the layer.
(DerivedShapeStore.Shape, DerivedShapeStore.ShapesInRegion)
(DerivedShapeStore.ShapeType, DerivedShapeStore.NumShapes)
(DerivedShapeStore.BoundingBox): New. DerivedShapeStore
equivalents of the new shape methods. These versions are simply
delegated to the original shapstore.

* Thuban/Model/layer.py (SHAPETYPE_POLYGON, SHAPETYPE_ARC)
(SHAPETYPE_POINT, Shape): Removed. They're now in data.py
(Layer.SetShapeStore): Removed the initializatin of instance
variables that were needed for the stuff that's now in
ShapefileStore
(Layer.BoundingBox, Layer.NumShapes, Layer.ShapeType)
(Layer.Shape, Layer.ShapesInRegion): Simply delegate to the
shapestore.