Ensure the target location can be pathed to by all units in the squad, so the squad won't get stuck if some units can't make it. Improve the choice of leader for the squad. We attempt to a choose a leader whose locomotor is the most restrictive in terms of passable terrain. This maximises the chance that the squad will be able to follow the leader along the path to the target. We also keep this choice of leader as the squad advances, this avoids the squad constantly switching leaders and regrouping backwards in some cases.
1. Optimize & move "ammo" related function from "AirStates.cs" to StateBase.cs
2. Optimize & move "IsRearm" function from "AirStates.cs" to StateBase.cs, name changed to "IsRearming"
(optimized by reaperrr)
