Adam's Advanced Nitrous | Staged Nitrous Systems Per Gear 1.2.0

Updated the mod to show MPH and HP added instead of Meters/Second for speed and KW for the power added.
Added the option to revert back to the metric system for people who still prefer it.

Thanks again to @AdamBlack for upgrading our nitrous systems! New functionalities and a repair for the beloved multi-stage nitrous sytem!