RuledSurface fixes, Switch Part_Mirror to SVG icon

RuledSurface fixes,
  claim children
  correct tool tip
  change default name from "Filled_shape" to "Ruled Surface"

Part_Mirror
  Switched icon in the tool bar, menu, and tree from
  the existing PNG icon to the also existing SVG icon

src/Mod/Part/Gui/Mirroring.cpp

@@ -182,7 +182,7 @@ TaskMirroring::TaskMirroring()
 {
     widget = new Mirroring();
     taskbox = new Gui::TaskView::TaskBox(
-        Gui::BitmapFactory().pixmap("Part_MirrorPNG"),
+        Gui::BitmapFactory().pixmap("Part_Mirror.svg"),
         widget->windowTitle(), false, 0);
     taskbox->groupLayout()->addWidget(widget);
     Content.push_back(taskbox);