Changes in ObserverSwarm.m
Need to catch the display message from each agent and implement new drawing method
worldDisplay = [ModObject2dDisplay createBegin: self];
[worldDisplay setDisplayWidget: (id <Raster>) self];
[worldDisplay setDiscrete2dToDisplay: [modelSwarm getWorld]];
[worldDisplay setObjectCollection: [modelSwarm getPlayers]];
[worldDisplay setDisplayMessage: M(drawSelfOn:)];
[worldDisplay setSizeFactor: sizeFactor];
worldDisplay = [worldDisplay createEnd];