Add newbackends/reuse KPublicTransport

[Thaodan]

While looking to add/fix Finlands Public Transport System in Fahrplan. I've looked to through Öffis backend library and then finally KPublicTransport.

Maybe it's easier to adopt KPublicTransport instead of writing our own parsers.

• https://gitlab.com/oeffi/public-transport-enabler (written in Java but could be still helpful)
• https://invent.kde.org/libraries/kpublictransport

[poetaster]

Since I'm working on the dbahn issue, I had a look at kpublic again and it's one of those problems that ripples through all projects. Where the dbahn backend is concerned, they still use the hafas mgate approach, which is also going to 'go away'.

Since it looks like the whole kde stack is going to transitious as a backend, I guess it'd be worth checking back. But for now, we can't use transistious since it doesn't do enough 'real-time' data for delays and such.