Adds Gun Turret MK2–MK5 as static upgrades (+2 range & +2 shots/sec each tier). Adds a mod option to add +4 range to all variants. No runtime scripts. Roman numeral overlays.
I saw a mod name "Turret Range Research",and like it, but it only support first tier of gun turret. Also how about new tier for lazer and allow player to config extra turret range as bonus.
