[PATCH] adding some collective behaviour of wild animals when attacked

[mimo]

The present behaviour of animals is quite odd : when an animal is attacked, either it flees or attacks, but none of the animals around react while we would expect that all animals around will react to the agression either by fleeing or defending the member of their herd. This is implemented in the patch attached. This could still be improved because I've not find how to determine that two animals are from the same specy. For the time being, I use their specificName but there are cases (elephant and elephant calf) where this would not work. Is there an unambiguous way to solve this question ? This patch works much better with the fix of #1723