NPC Spell AI Casting Changes

[demonstar55]

I added a special case for priority 0 spells. This new special case basically emulates what we believe EQ devs call "innate spells."

NPCs with innate spells will try to spam these on their reuse timers. Ex. Lord Naggy's AE fear is always cast on recast timer. You should be able to count on it.

Most of normal EQ mobs function like this and eliminates the need to use quest scripting.

I also added support to define a valid HP range an NPC will cast a spell. The min_hp field is the low end of the range and max_hp field is the high end. For example, lots of mastruqs in GoD will cast Protection of Discord at low HP, setting max_hp will allow the NPC to not cast this until they reach this percentage. This range is also purely based on the caster's HP ratio.