We'll create a scoped service provider if the middleware that does it
isn't there.
We resolve all of our stuff from the scoped service provider, allowing
users to plug in any scoped things they want.
Ported UrlHelper to be a scoped service.
This follows a similar pattern to html helpers - a minimal basis interface
that performs the main functionality, and a set of extension methods that
make up the rich API.
Ryan Nowak