Enable usability of atmodat data checker on Windows

[atmodatcode]

This was a request from the METOOLS.

Apparently, in Windows 10, Ubuntu Linux can be easily installed. We should check this out and see if the atmodat checker can be installed and executed there.

Alternatively, METOOLS participants asked for a atmodat data checker GUI for WIndows
or a web interface where one can upload a file and where the checker results are displayed online, similar to what is available on http://pumatest.nerc.ac.uk/cgi-bin/cf-checker.pl

[jkretz]

As proposed, one option would be the Windows Subsystem for Linux (WSL) with which I had made good experiences so far and which is relatively easy to set up.
Nevertheless, a native Windows version would be nice. Up to now, we did not invest time into verifying that the checker is working on Windows, but I will have a look at it.

[jkretz]

After some minor adaptions to the checker, I was able to run it on Windows. I will start working on it once the two open PRs have landed.