Add extension method: VaultPropertyDefOperations.GetOwnerPropertyDefID

[CraigHawker]

Would be a shorthand for this sort of code.

            // Get the owner Mandant propertyDef
            ObjType owningObjType = env.Vault.ObjectTypeOperations.GetObjectType(Configuration.Identifier.ObjectType.Mandant);
            int besitzerMandant = owningObjType.OwnerPropertyDef;

Should take a single integer parameter for the object type ID.