Adjusted preview image.

Fixed flatbed and fueltruck version behaving weird on bridges.
Adjusted wheel meshes.
Changed preview image.

Fixed LODs in covered variant.

Adjusted some numbers in covered hull variant, so it can actually carry 20t

Added covered hull variant.
Small model adjustemts.

Changed entry date of firetruck variant (1967 -> 1973)
Changed firefighting skill of firetruck varaint (35 -> 40)
Removed ability to carry boards for logger varaint to keep consistency with vanilla vehicles
Changed woodcarrying skill for logger variant (33 -> 37)
Changed woodcarrying skill for open hull varaint (22 -> 25)

Fixed rear blinkers in dumper variant

Adjusted wheel proportions and other small fixes