Tractor with trailers in traffic v3.0

Replaced tractor with new model with beacon lights and tube smoke.
Added new trailers – log trailer and empty log trailer.
Reduced spawn ratio to 0.1
Tractor speed limits 40 km/h
Old trailers use also.

Thanks very much to Todor Alin for tractor and log trailer models.
I thank him for his patience with my requirements by model.
Thanks to AlexeyP for rework default trailer for this mod.