Support data formats in download

[nuest]

The API supports several ouput formats (shp, csv, rdf) which should be accessible easily via the importEnviroCar method.

New demo importFormats shows how these different outputs look and that they can (partially) be re-used in R.

[staschc]

For the import, it's sufficient to use just one format. As soon, as data is available as TracksCollection or Track object, the used format for import does no longer matter.

[BenGraeler]

How about performance issues? I'd imagine csv to be the fastest way to import many tracks.

[staschc]

Yes, it's probably good to switch to CSV.

[nuest]

It's just a few lines of code to support other formats, and open source people have weird tool combinations... so if I'm and R+QGIS user, I might use R to download a shapefile to open in QGIS...
Anyway, I see your point that we should have one that works really well, which imho should be the JSON because there is more metadata in that than can be carried in the CSV (e.g. about the car). But for someone who doesn't need that metadata we can demonstrate the other formats, e.g. CSV.