Improve common settings property grouping.

Also moves apply-icon-scaling-to-fonts to its own checkbox.  (We used
to try to infer when to do it, but that turns out to be a rathole.)

common/dialogs/panel_setup_netclasses.cpp

@@ -136,7 +136,7 @@ PANEL_SETUP_NETCLASSES::PANEL_SETUP_NETCLASSES( PAGED_DIALOG* aParent, NETCLASSE
         attr->SetEditor( new GRID_CELL_ICON_TEXT_POPUP( g_lineStyleIcons, g_lineStyleNames ) );
         m_netclassGrid->SetColAttr( GRID_LINESTYLE, attr );
 
-        m_colorDefaultHelpText->SetFont( KIUI::GetInfoFont( this ) );
+        m_colorDefaultHelpText->SetFont( KIUI::GetInfoFont( this ).Italic() );
     }
     else
     {