(PUP-3462) Hiera scope: add the key 'calling_class_path' 

calling_class_path is calling_class with :: replaced by a /

This enables to have the class hiera yaml files in directories and enables to have class based hiera data on windows which does not allow ":" in path names.
Cool. Would you see a case for another way so the files can continue to be in the top level folder? I'm failing to come up with something that would not conflict with naming. Underscores are out to me. So maybe directory is best.