Give access to qTip callbacks

I am attaching the patch. Some modifications:

• Predefined beforeShow callback is called inside init() function. It should fix some bugs like #1077778: Automodal links not working in Menu Minipanels?
• Class menu-minipanels-processed is added, after Drupal.behaviors is applied to target #1025450: JS should add a processed class to menu items which have already been proceseed
• There is a function MenuMiniPanels.setCallback, which can register own qTip callback

  Example. This code can be placed inside your own javascript file. It show alert dialog, when qTip is shown.

         MenuMiniPanels.setCallback('onShow', function(qTip, event, content) {
            alert('onShow');
         });