get productversion of terminal.gui not version (#1163)

UICatalog/UICatalog.cs

@@ -162,7 +162,7 @@ namespace UICatalog {
 			aboutMessage.AppendLine (@" |___/                   ");
 			aboutMessage.AppendLine ("");
 			aboutMessage.AppendLine ($"Version: {typeof (UICatalogApp).Assembly.GetName ().Version}");
-			aboutMessage.AppendLine ($"Using Terminal.Gui Version: {typeof (Terminal.Gui.Application).Assembly.GetName ().Version}");
+			aboutMessage.AppendLine ($"Using Terminal.Gui Version: {FileVersionInfo.GetVersionInfo (typeof (Terminal.Gui.Application).Assembly.Location).ProductVersion}");
 			aboutMessage.AppendLine ("");
 
 			_menu = new MenuBar (new MenuBarItem [] {