[QOL] When exchanging a SLF for another, ask if the livery should be kept (except paintjob)

[Julio Montega]

Ahoy there,
when you test out different SLFs or loadouts, you always have to set the livery up anew.
Why not just ask the user, if the livery, excluding the paintjob, should be kept.
That's save some hassle.