make Resource.incoming_value_flows() method work for Dhen
make Resource.incoming_value_flows() method work for Dhen

valnet/valuenetwork,FreedomCoop/valuenetwork,django-rea/nrp,thierrymarianne/valuenetwork,thierrymarianne/valuenetwork,django-rea/nrp,valnet/valuenetwork,valnet/valuenetwork,FreedomCoop/valuenetwork,django-rea/nrp,django-rea/nrp,valnet/valuenetwork,thierrymarianne/valuenetwork,FreedomCoop/valuenetwork,FreedomCoop/valuenetwork,thierrymarianne/valuenetwork