[WIP] vehicle menu tweak

Guys, that's my first experience in cpp, so all comments are really welcomed. Also, I can't compile current windows build due to some json errors, so I would ask @Cata-Jenkins to compile it before release. The main idea is to tweak code of vehicle menu, and [partially] fix the issue #3031 (even pre-defined names of some cars like military cargo Truck looks bad now).
Grab the correct string from the units options for display.
Clarify vehicle construction menu layout code, and steal some space for the status display from the items list.
Shuffle around members of vehicle construction menu to make room for everything.