Added support for .crit_power (percent) field to weapon combat, which adds to the critical multiple for (only) attacks with the weapon.
Applies to melee, unarmed, shield, and ranged attacks.  Object descriptions and character sheet updated.

Throwing Knives talent uses this new field (to avoid permanent changes to crit power on errors).

Slightly nerfed Lure durability so normal NPC's can more easily kill it at high level.