OpenOrders (and sub content) Where instances of Orders.
Restore this property to not break current implementation,
even if the question "OpenOrder are Orders or not ?" stay open.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@43215 20353a03-c40f-0410-a6d1-a30d3c3de9de