This class handle inheritance as 1-1 association based on a anonymous field
(no field in persistent object needed).
version: $Id: SuperReferenceDescriptor.java,v 1.1.2.6 2005/12/21 22:26:10 tomdz Exp $
If this method returns true the inheritance described by this object
is a normal JAVA inheritance. If false the inheritance is only declared
in the O/R mapping it's a declarative inheritance, the referenced "super class" in not
a JAVA super class of the main class.