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.
a06cb8fccb