Add support for the changed Bahntransport Logo

[Mimoja]

The bahntransport is now exported as an icon below the security code. To ensure we dont render over any previously rendered images we add a small helper to check if the target area is available to render into

[Mimoja]

In the final render it looks like this:

[typingbeaver]

Will take a look into this! -- Didn't even know if it still existed.

I think the new regulatory weight markings (10+ kg and 20+ kg) are in it's original place now.