* Support loading parts through an assembly metadata attribute with a
key of Microsoft.AspNetCore.Mvc.AdditionalReference and a value that
describes the additional assembly to add to the list of parts and
whether or not it should be added by default. The additional reference
can only contain the file name of the assembly and it must be located
side by side with the assembly where the additional reference is
defined.
* Add an AdditionalAssemblyPart application parts to represent parts
that are not part of the original application per se, like precompiled
views.
* Update the ViewsFeatureProvider to search for razor views in the
application part directly instead of trying to load the precompiled
views assembly part.
