Draft: fix front page issue
actually the front page is broken when Access Tab Front Page is enabled
It's because erp5_wendelin_configurator is now in the default_bt5, and it has ERP5Site_createDefaultKnowledgeBox which refer to portal_gadgets/WendelinInformationGadget present at erp5_wendelin
so if erp5_wendelin is not installed, we'll have such error
i propose to move ERP5Site_createDefaultKnowledgeBox to erp5_wendelin