Attribute route link generation will now have a slight preference for
entries that can use ambient values (vs ignoring an ambient value). This
means that areas will be more 'sticky' with regard to link generation
without the need to specify a better Order.
This change makes the attribute route capable of responding to updates in
the action descriptor collection.
The change moves the actual route implementation to InnerAttributeRoute.
AttributeRoute now wraps an InnerAttributeRoute - when processing a route,
AttributeRoute will now check with action descriptor collection if its
InnerAttributeRoute is still 'current' and rebuild it if necessary.
Kiran Challa
ianhong
N. Taylor Mullen
Ryan Nowak