eventDragStart ============== Triggered when event dragging begins.
function( *event*, *jsEvent*, *ui*, *view* ) { }
`event` is an [Event Object](../event_data/Event_Object) that hold the event's information (date, title, etc). `jsEvent` holds the native javascript event with low-level information such as click coordinates. `ui` holds the [jQuery UI object](http://jqueryui.com/demos/draggable/). `view` holds the current [View Object](../views/View_Object).