SVGHMI: widgets are not anymore binary relative or absolute, but have a "relativeness".

Because of allowing multiple variables per widget, we must distinguish if individual variables is relative to page, not the whole widget.

<?xml version='1.0' encoding='utf-8'?>
<BaseParams xmlns:xsd="http://www.w3.org/2001/XMLSchema" IEC_Channel="0" Name="bacnet_0"/>