fixes #23: Implemented common base class for comparable data types. Used in in NumericParamterDef and OrdinalParameterDef.
fixes #23: Implemented common base class for comparable data types. Used in in NumericParamterDef and OrdinalParameterDef.

FrederikDiehl/apsis,fdiehl/apsis,fdiehl/apsis,FrederikDiehl/apsis,fdiehl/apsis