SVGHMI: fix XY graph init (consequence of earlier change) + reindent

Earlier change did modify the variables attributes (options) are stored in widget objects. XY graph uses variables' min and max to determine range.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot URI_location="LOCAL://">
  <TargetType/>
  <Libraries Enable_SVGHMI_Library="true"/>
</BeremizRoot>