SVGHMI: Lighter display of HMI Tree, no more icons and use buttons. Auto expand root. Fix loading of HMI tree XML backup (hmiclass attribute wasn't kept).
<?xml version='1.0' encoding='utf-8'?>
<SVGHMI xmlns:xsd="http://www.w3.org/2001/XMLSchema" OnWatchdog="echo Watchdog for {name} !" OnStart="chromium http://127.0.0.1:{port}/{name}" OnStop="echo Closing {name}" WatchdogInitial="10" WatchdogInterval="5"/>