Simple system for specifying functions as menu items.

[andr3wmac]

Example usage:

    var mbar = new zebra.ui.Menubar({
           "Item 1": {
               "Subitem 1.1":null,
               "Subitem 1.2": function() { console.log("Item Pressed!"); },
               "Subitem 1.3":null
           }
       });