Add MVG Rad (Munich) again

[maledo]

Due to #239 MVG Rad was removed from the api. As far as I understand the comment @eskerda in the PR, there are links to the stations or the positions of the bikes available? So is it possible that they get added outside of nextbike.json again?

[martgnz]

I haven't found a good way to get bike data from the current MVG Rad site. Best lead I have so far is this map: https://move.mvg.de/?location/48.14003,11.56107

It seems that they're planning to replace it next year with a wider regional service so maybe that one will have a better place to get bike data: https://muenchenunterwegs.de/news/regionales-bikesharing-system-und-mehr-abstellflaechen-fuer-mikromobilitaet