values: sets how many times this unit may fire its AA guns. Defaults to -1, which means infinite. If not infinite, then aa guns can stack.
(If you have multiple aa of the same type-group in a territory, and they have different attack values or dicesides, and different maxAAattacks, then what happens is that the engine will roll for the best attack/diceSides and for the best maxAAattacks, even if that is two different units
For example, if you have an aa gun that has infinite attacks and rolls a 4/20, and you have another gun with only one attack and rolls 3/6, then you will end up rolling infinite times at 3/6. This might be fixed in the future.)