changed exchange graph to minimally query an arcs capacity
changed exchange graph to minimally query an arcs capacity

rwcarlsen/cyclus,Baaaaam/cyclus,gidden/cyclus,gidden/cyclus,mbmcgarry/cyclus,mbmcgarry/cyclus,hodger/cyclus,rwcarlsen/cyclus,Baaaaam/cyclus,mbmcgarry/cyclus,mbmcgarry/cyclus,rwcarlsen/cyclus,gidden/cyclus,hodger/cyclus,hodger/cyclus,rwcarlsen/cyclus,hodger/cyclus,hodger/cyclus,gidden/cyclus,Baaaaam/cyclus