Web Layout Editor loose ends

[jng]

The Web Layout editor in Maestro 3.0 has some loose ends that require fixing up:

• Adding new commands will correctly add the corresponding entries in the menus toolbar, but the labels are blank.
• The button in the Invoke URL command editor that should launch a layer selector does not work.
• Icons should be shown beside each command, or at least show icons for the custom commands (Invoke URL, Search, Invoke Script)