nodeGraph and updated info()

I've added the node graph functionality into the katRun object, as katRun.nodeGraph(). Give it a try, and if you like it, I'd be happy to see it merged :) Also, I slightly updated the katRun.info() function so that it now also displays the x location of minima/maxima -- might need further testing.

Warning: I had to remove the .gitlab-ci.yml file so that the project wouldn't show errors on gitlab, but of course you would want to keep this file. Not sure how to exclude that change from a merge request, though :-(