SVGHMI: Stop ignoring HMI_NODE in HMI tree, and count it as a BOOL. Soon we use those nodes as reference for relative page jump, and as an "enable" bit for features associated to an HMI tree fragment.

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