Add statistics panel

[tordans]

I would be interesting to see some count and length statistics.
Maybe as part of the home panel.
Maybe with sub-groups per 'Bundesland'.
And maybe with the same number for 'Autobahnen' to provide some context.

PS: Great projects, thanks

[ohrie]

Thank you for the comments!
Actually it's not that easy, to sum the length of all ways. For most of the ways there is only a estimation, since the planning is not finished yet. Therefore only some of the ways have the lenght attribute in the GeoJSON (see https://github.com/ohrie/radschnellwege).

But in future, this would be cool!