Split up primitive binding and ease-of-use portions

[Dridus]

Right now there's a bit of duplication and inconsistency in the naming when there's a primitive binding version of something, e.g. ReactSpec, Props, and an ease-of-use layer on top, e.g. Spec, Properties.

To clarify it, move the primitive bindings to React into React.Primitive and remove the React prefix from each, e.g. ReactSpec would be moved to React.Primitive.Spec.

The React module would then be the home for the ease-of-use layer, reexporting whatever primitive binding functions made sense.