Implement Cylinder.
Implement Sphere.
Change from_ruby_pnt2d to from_ruby<gp_Pnt2d>.
Add from_ruby<gp_Vec>.
Add from_ruby<gp_Dir>.
Implement Shape.rotate (move code in common with Shape.move into
a separate function).
Refactor Shape creation from shape_transform into wrap_rendered_shape.
Implement Shape.scale.
Sphere should be called Sphere, not Shape. Oops. :)
Implement Torus.
Move Box.initialize into Ruby-space, leaving render in C++.