- improve existing superClasses() via using transform (internal it uses
   reserve, shorter, ...)
 - remove unused superClassNames() if necessary it can be done by a
   simple transform call
 - introduce and use classHierarchy() and fix foreach loop which was using
   wrong "modelNode" instead of "superClass"

Change-Id: Ia52bcbd322f3a047a020faf4a67aca2a1b8fd19a
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>