SVGHMI: In order to allow widget signature and description to coexist in same ysl2 file, introduced widget_class, widget_defs to declare widget codegen templates and gen_index_xhtml to mark templates that are only usefull in gen_index_xhtml.xslt.
<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot URI_location="LOCAL://">
<TargetType/>
<Libraries Enable_SVGUI_Library="true" Enable_Python_Library="true"/>
</BeremizRoot>