What Kitti dataset are we supporting?

[NicolasHug]

We added support for the Kitti dataset in #3640 but it's not clear which one we are vendoring, as there are many different versions of the dataset : http://www.cvlibs.net/datasets/kitti/index.php

@pmeier @fmassa @prabhat00155

[NicolasHug]

After a bit of trial and error, looking at the URLs it seems to be the "left color images" dataset for object detection