Changes

Trailer cargo definition files ("/def/cargo/<cargo_name>/<trailer.cargo>.sii") got two new array attributes, : '''cargo_mass_ratio''' and '''cog_offset'''. The cargo mass ratio array defines how cargo weight and forces are distributed among master and slave trailers (each array item is of type float). Additionally, the center of gravity array then defines offset of center of gravity in all directions (each array item is of the type float3).