Extends push and pop mecanism to both ReportSection selection and form
listbox's selection, as the listbox will edit the form's selection.
This is only usefull if the selection used in a ReportSection is not the same as
the selection used by the ERP5Form for this ReportSection.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@3052 20353a03-c40f-0410-a6d1-a30d3c3de9de