Make Casters Blue

Added Plater's detection: caster = NPC whose UnitClassBase is "PALADIN" (how WoW tags mana-using NPCs internally), with the old mana-pool check kept as fallback.
Fixed the cache bug: negative "not a caster" verdicts are no longer cached, since one bad early read used to blank that mob type for the whole session — this was the likely cause of your uncolored dungeon mobs.
Version bump to 2.0.2.