Actor previously cached targetable locations for static actors as an optimization. As we can no longer reference the IPositionable interface, move this optimization to HitShape instead. Although we lose some of the efficiency of caching the final result on the actor, we gain some by allowing HitShape to cache the results as long as they have not changed. So instead of being limited to static actors, we can extend the caching to currently stationary actor.
* Adds support for linking Armor traits to HitShapes.
* Adds spread support to TargetDamageWarhead
* Removes ring-damage support from HealthPercentageDamage
* Removes IsValidAgainst check from DoImpact(Actor victim...) overload
and instead lets warheads perform the check beforehand
(to avoid HitShape look-ups on invalid targets).
* Reduces duplication and improves readability of Warhead implementations
And remove ITargetablePositions from Building.
Also, added UseFootprintOffsets to replicate the old Building behavior for easier setup of TargetablePositions for buildings.
