Integration with overlay2

[strowk]

It's a little bit hard to locate the layer on the disk using information from docker image. The way overlay2 for instance works is that layers have a links to each other in a files and to find a particular layer one has to go through a lot of files.

This could be automated and I think it would be nice if dive could do it. Specifically one feature could be convenient - output somewhere path to the overlay2 folder with layer contents, so that we could cd there from f.e. mc and look inside of the files.