Correct targeting for small arms dmg type

[pvutov]

Turret system currently wont lock onto soft vehicle targets if a unit only has small arms weapons. The issue is in Ammo.cs, GetRangeAgainstTargetType. However it also has to do with how we currently pick targets. Ultimately the issue is that we should only pick vehicle targets if they are facing us with a <2AV side, and drop them if they stop facing in this way (currently we never really drop the current target).

Obsolete, old description:
When defining the damage types I forgot to include small arms.

We need to add a small arms option to the unit config, a small arms damage type in Ammo.cs, and a small arms formula in ArmorComponent.cs. This damage type doesnt have an explosion radius, does 10% damage against 1AV and no damage to 2AV.

Might need a heavy small arms type which follows the same rules but does 50% damage against 1AV.

Also we might need to do this with an AoE tag if we want to allow cluster..