plugins/nsevents: Add back destroy object hook.
plugins/solstice: Remove destroy object hook.
plugins/combat: Add removing creatures from the cache.

- Add code to listen to nwnx_(ns)events plugin events.
- Add supporting code
plugins/solstice: Fix debug level in Handle_ConversationEvent.
plugins/solstice: Add GetTotalFeatUses hook.
plugins/solstice: Clean up Hook_GetFeatRemainingUses
plugins/solstice: Add nwnx2.ini and some support code for reading settings.
plugins/solstice: Statically link luajit... for now.