Fix: https://github.com/aspnet/Scaffolding/issues/65

The root cause is that ‘dynamic’ does not work if the underlying object is internal with beta Roslyn bits. [I know this worked in alpha4]

So the fix is to simply make the class (template model used for empty template) from internal to public.

[Since this used to be a shared class in a shared project, I had to remove it from shared project and make copies in the actual projects that used it]