and not old JS files cached by the browser.

What would be done is:

1. An Ametys URL responding the current Ametys version
2. Load ASAP a JS file containing the current Ametys version, asking this URL and compare the values
   => if same values, do nothing more (JS files are up-to-date)
   => if not, the JS files are ones cached by the browser (outdated). Display a popup warning the user of it and advise him to clean its browser cache (no other way??) and reload the page