Renault Premium 6x2-4 ja 6x4 paranneltut akselistot

Moved box on left side as far forward as possible, flipped ladder.
- Shrank and moved left side fuel tank.
- Deleted small tank, shrank and moved right side fuel tank.
- Added second axle, stretched chassis, moved trailer hitch.
- Repositioned driveshaft to clear and meet second axle on the 6×2-4 and
- 6×4 chassis respectively.
- Modified shadow-casting meshes and collision shapes.
- Flipped mounting point on a small handle to clear the new axle.
- Edited UI shadow texture to add the extra wheels.