Fix a issue that BusinessTemplate unexpectedly removes the skins of another skin folder when upgrading. To fix the issue, (un)restrectedTraverse calling are replaced with the new method, (un)restrictedResolveValue.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36841 20353a03-c40f-0410-a6d1-a30d3c3de9de