Maintenance fixes to keep the project useable.

[marcor]

Put some effort in making this nice software work on a Guix installation. (Almost there.)

I had to try and fill the gap between the repo and the latest available release on openmolar.com.

Several tests will raise errors because some of the test data is not available in the demo dataset.

[marcor]

For reference: https://lists.gnu.org/archive/html/bug-guix/2024-02/msg00096.html