add interface attribute
add interface attribute

TheVirtualLtd/bda.plone.cart,andreesg/bda.plone.cart,andreesg/bda.plone.cart,TheVirtualLtd/bda.plone.cart,andreesg/bda.plone.cart,andreesg/bda.plone.cart,TheVirtualLtd/bda.plone.cart,TheVirtualLtd/bda.plone.cart