by seb: commit jp's change, add property grouping_reference

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@3168 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/PropertySheet/Reference.py

@@ -48,6 +48,10 @@ class Reference:
             'description' : 'The references of the document for default destinations',
             'type'        : 'string',
             'mode'        : 'w' },
+        {   'id'          : 'grouping_reference',
+            'description' : 'A reference which allows to unify multiple objects',
+            'type'        : 'string',
+            'mode'        : 'w' },
         {   'id'          : 'document_reference', # XXX ERROR - we already have a reference
             'description' : 'The references of the document itself',
             'type'        : 'string',