workshop 3/6

1. Altered "nbrCages" in class Zoo to const

2. Created isZooFull method that verifies if a Zoo is full or not by pointing on nbr animals and nbrCages

3. Created « Zoo comparerZoo(Zoo z1, Zoo z2) » in class Zoo keepin in mind that z1 and z2 are type Zoo as parameters that return Zoo with the highest animals