Add a resource_facade intrinsic function to HOT

Add a native version of the function, rather than continue to rely on
Fn::ResourceFacade from the Heat-flavoured-cfn templates.

Closes-bug: #1299205

Change-Id: Iee118aeaa72d59e4d6a27ed487b99e9aba9779cd
Merge "Add a resource_facade intrinsic function to HOT"