Transport Fever 2 - US Diesel Train Overhaul

Replaces sounds and modifies introduction dates as well as horsepower & tractive effort for some built-in US diesel and electric locomotives engines to be more accurate. Also adds EMD GP7 as alternative to the GP9. Bells ring at low speeds, engines will idle when stopped. Trains using train_diesel.lua have sounds replaced with EMD 16-645 engine.

Credits:Howdy Hondas Memorial Day Sale E