SVGHMI: Filter unseen geometry from inkscape CSV output.

When inkscape exports geometry form all objects, then it also includes objects from svg:defs. This makes problems when deciding if an object is part of a page, since coordinate of objects in svg:defs can eventualy be contained in a page. In the end, those objects where getting detached when leaving pages where they where found, leading for exemple to non working text on clipping when the clipped text was cloned in multiple page.

// widget_back.ysl2

template "widget[@type='Back']", mode="widget_class"
    ||
    class BackWidget extends Widget{
        on_click(evt) {
            if(jump_history.length > 1){
               jump_history.pop();
               let [page_name, index] = jump_history.pop();
               switch_page(page_name, index);
            }
        }
        init() {
            this.element.setAttribute("onclick", "hmi_widgets['"+this.element_id+"'].on_click(evt)");
        }
    }
    ||