Railway station ID confusion (uic_ref)

Sound good to also include those. As far as I can check these ids do not align with uic nor ibnr. So for Hamburg Hbf its: DE14393.

I still believe there is some value in migrating uic_ref to ref:uic as currently most of the station do have uic_ref, so its more about clarifying whats actually there, while aligning with a namespaced key schema. The alternative would be to add another key or rely on a ref:ibnr as an indicator that both ids have been checked correctly.

As a next step I would now add a ref:ibnr key to some major stations in Germany and adjust ref_uic to the actual uic code to see if there is someone complaining.
Additionally I would update the wiki article to address the difference between IBNR and UIC correctly.