DeMo suite : improvements / bug fix

The DeMo suite is used to track DQ defect evolution. See typical outputs here : https://atlasdqm.web.cern.ch/atlasdqm/DeMo/YearStats-2022-Tier0_2022.html This is a standalone suite. No software depends on it. I am the original developer and I tested extensively the latest version (daily cron job to produce the plots automatically). It contains several bug fix and improvements to make it more robust and easy to maintain.