Add a proxy role, this script must be able to set the reference even if the current logged in user does not have modify permission on the document (if he can pass the transition, it's OK)

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@21018 20353a03-c40f-0410-a6d1-a30d3c3de9de