- standardize on the `Type` extension method; less verbiage
- `ModelMetadata` had a redundant `IsAssignableFrom()` call
- `ModelBindingHelper.ValidateBindingContext()` over-engineered and used just once
- do useful bit inline in `KeyValuePairModelBinder` but now a silent "does not apply" case
* Moved instantiation of view components into DefaultViewComponentActivator
* Introduced IViewComponentFactory to handling setup of new view component instances.
* Added a release method on IViewComponentActivator for handling tear down of view
component instances.