Limit attack helicopters

By default, there's two slots that users in the same faction can take to spawn attack helicopters. By default there's a 720 (12 min) cooldown for each slot whenever a helicopter gets destroyed (or drowns). The cooldown is global, for the whole server. There's 2 slots for attack helis.

Works for:
AH1S
AH64D
AH6M
KA52
Mi24
Mi8MT (gunship)
UH1H (gunship)