(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.
yes.

example class:
profile::firewall::rule

hiera.yaml hierarchy with yaml backend:

class/%{calling_class}: 
evaluates to path class/profile::firewall::rule.yaml which is not allowed on windows. 

class/%{calling_class_path}:
evaluates to class/profile/firewall/rule.yaml which is more or less the same what happens within the manifest lookup for classes (e.g. profile/manifests/firewall/rule.pp)