Use new API endpoint

Apparently DB changed the endpoint of their onboard data API (see commit 51ce3df), but it's not quite sure if that's a universal change on all trains or only on some that run a different version of the onboard portal.

If it's the former, everything should be working fine, if it's the latter, the built-in proxy will need to be changed.

v0.1.0

Use the tileserver that's accessible from the captive portal