Add ModelBinderAttribute

[rynowak]

We need to add ModelBinderAttribute to the core framework.

This is an attribute that allows a user to specify a specific model binder for a type by attributing a type, or parameter. With uberbinding it probably also means properties are allowed. The attribute specifies a model binder by type.

There's a version checked in to webapi, but it only serves to mark a type as model-bound, an doesn't allow you to specify the binder.

The legacy WebAPI version has a few more knobs. We should investigate if they are relevant.

[rynowak]

e9bcc3f