Implemented isNationPVPZone() zone check, to ensure only PVP between players of the opposite nation (arenas, for instance, allow both).
Game server: war boolean flags are now expressed as such (otherwise it just looks like there's more states than just 0 or 1).
Game server: rewrote CUser::ZoneChange() checks. These still do not include the correct error responses, but it's a start. Refs #256.