Proposal for Rect / Rectangles

Adding the name Shape to the end of all class names for all “shapes”
seems awkward. Here’s a proposal that does the following:

Structs are named by removing the CG prefix: CGRect -> Rect, CGSize ->
Size, CGPoint -> Point, where Rect contains a Point and a Size

This allows us to use the name Rectangle for the actual shape class,
and from here we can call shapes by their names: Triangle, Line,
RegularPolygon (or Polygon), etc.