Many additions to 900bc06d2c236b:
 - Fix indentation
 - Consider any kind of light, not just torch_infinite_time
 - Hostile NPCs should also wear lights, if they have nothing else that could use the slot (or a twohanded weapon)
 - Remove redundant code and don't add additional lights to the inventory
 - World::isDark returns false for interiors which are unaffected by weather