Apply XDT transformation to non-.config XML files

[stimpy77]

A user has requested support for applying transforms to any .xml file and not just .config files.

[haliphax]

Would be nice if we could run these against *.config files, and not just Web.config or App.config. I am working with a delivered enterprise application that uses App_Data/settings.config with transforms, and we can't test them locally without a build/publish.