Predator problem comments

If you place the PredatorFish class with the other MBS code and 
make the appropriate change in the MBSGUI class so that it recognizes 
the PredatorFish and has a different drawing for them, then this
can easily be tested. If you use the original version of the Fish
it can be a little easier to see what is happening, since the Fish
will not die of natural causes, only from getting eaten or, for
the predators, starving.

