fix findSpecialiseValueList so that now it works with portal_type_list
parameter and an inheritance tree bigger than 3 levels

and also fix a problem in findEffectiveSpecialiseValueList which was
addind None object to result list


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31287 20353a03-c40f-0410-a6d1-a30d3c3de9de