Add a workaround for CSG failures with some OCC objects.
Support 2d move() and scale().
Add regPoly() (like regPrism() but 2D).
Reimplement regPrism() as an extrusion of regPoly().
Fix regPoly() so it correctly passes 2D points to Polygon, rather than 3D points.
Add Object3D._moveApply(); implement cylinder(center=) with it.
Add LinearExtrusion(center=) parameter.
Support subscripts (e.g. array[0]).
Fix support for 2D vectors in scale().
Allow Object3Ds with shape=None (i.e. empty combinations) to be
transformed or included in other combinations.