itemprop: Fix missing module table.
creature/ability: nil not convertible to bool.
nwnx/effects: Modify API such that effect handlers must return two values, one for deletion, one for suppression.

This is necessary since most effects have their icons applied on application, suppressing by default would lose those.
Integrate nwnx_combat and nwnx_solstice.

There have been a huge number of changes for performance reasons.
* Ranged / Melee Attacks have been completely redone.
* Rules for determining hitpoints, special attacks, and combat situations have been added.
* Rules for determining the number of onhand and offhand attacks have been added, as well
  as for initializing a combat round.  NOTE: These are not default rules.
* Damage resistance and immunity have been redone.  The no longer accept damage flags, only
  damage indexes.
* Maximum hitpoint hook has been added, allowing for healable hitpoint effects.
* Effects: DamageIncrease and DamageDecrease have been expanded to allow effects that are unblockable
  and/or applied only on critical hits.  NOTE: Damage that had previously been unblockable will not be by
  default.  To fix this NWScript side would require nwnx_structs.
* The object cache has been redone...
* Fix BAB calculations for non PC creautres.
* Many other things...
Merge branch 'feature/combat'