add all_suppliers method to EconomicAgent
add all_suppliers method to EconomicAgent

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