Add in a prevent drag drop in the floating panel menu.  #10373

A patch for http://dev.ckeditor.com/ticket/10373

I left the configuration CKEDITOR.config.disableMenuDrag as false by default since I was not certain somebody did write a plugin that _did_ allow you to drag images or something into the editor.

This will prevent drags from the menu in most recent browsers (they do need an on dragstart event).   In addition another option is to to add in this css to the iFrame body, but that probably only works in FF and Chrome.

//Css for the body of the iFrame if that route is preferred.
-moz-user-select: none;
-webkit-user-select: none;