Tweaked RA and TD artillery explosion

Renamed RA UnitExplode to AmmoExplode, added new UnitExplode with 1/10
damage.
Reduced TD UnitExplode damage to 1/10 of old value.

Now artillery always explodes, but there's only a 75% chance it explodes
violently and only when it has ammo.
If either condition isn't met, it explodes with the (now less violent) UnitExplode.

mods/ra/rules/vehicles.yaml

@@ -226,8 +226,9 @@ ARTY:
 	AttackFrontal:
 	WithMuzzleFlash:
 	Explodes:
-		Weapon: UnitExplode
-		Chance: 75
+		Weapon: ArtilleryExplode
+		EmptyWeapon: UnitExplodeSmall
+		LoadedChance: 75
 	AutoTarget:
 	ProducibleWithLevel:
 		Prerequisites: vehicles.upgraded

mods/ra/weapons/explosions.yaml

@@ -197,6 +197,25 @@ UnitExplodeSmall:
 		ImpactSound: splash9.aud
 		ValidImpactTypes: Water
 
+ArtilleryExplode:
+	Warhead@1Dam: SpreadDamage
+		Spread: 426
+		Damage: 150
+		Versus:
+			None: 90
+			Wood: 75
+			Light: 60
+			Heavy: 25
+		DamageTypes: Prone50Percent, TriggerProne, ExplosionDeath
+	Warhead@2Eff: CreateEffect
+		Explosion: self_destruct
+		ImpactSound: kaboom22.aud
+		InvalidImpactTypes: Water
+	Warhead@3EffWater: CreateEffect
+		Explosion: large_splash
+		ImpactSound: splash9.aud
+		ValidImpactTypes: Water
+
 BarrelExplode:
 	Warhead@1Dam: SpreadDamage
 		Spread: 426