Refactors LimitedAmmo to AmmoPool.

Removes Reloads trait.

This enables adding multiple AmmoPools via @ differentiators and
Name which adds the possibility to assign each armament to a specific
ammo pool.

Furthermore, this moves all Reloads functionality onto AmmoPool.

Now a combination of all three is possible on a single actor: no limited
ammo, limited ammo that can reload on its own, and limited ammo which
needs to be reloaded at a rearm actor.

Additionally moves RearmSound from Minelayer to AmmoPool.

OpenRA.Mods.Common/Scripting/Properties/PlaneProperties.cs

@@ -45,7 +45,7 @@ namespace OpenRA.Mods.Common.Scripting
 		[Desc("Fly an attack against the target actor.")]
 		public void Attack(Actor target)
 		{
-			Self.QueueActivity(new FlyAttack(Target.FromActor(target)));
+			Self.QueueActivity(new FlyAttack(Self, Target.FromActor(target)));
 		}
 	}
 }