Move common DoImpact(Target) method into DamageWarhead.
Remove more unnecessary plumbing.
Move warheads into mod code.
Convert weapon plumbing to use integer damage modifiers.
Further warhead streamlining.
Change EffectivenessAgainst to CanTargetActor.
Remove fp calculations from SpreadDamageWarhead.
Remove now-redundant AbsoluteSpreadDamageWarhead.
Convert versus to integers.
Increase falloff accuracy for large damage amounts.
Fix inner range filtering in HealthPercentageDamageWarhead.
Adds Diplomacy keywords for ValidTarget checks.

Changes:

Allows diplomacy stance checks to be done on warheads and weapons, using keywords in ValidTargets and InvalidTargets.
Ioncannon changed to AbsoluteSpreadDamage.