fires when the user drags/resizes events in the scheduler
| id | string | the event's id | 
| mode | string | the dragging mode: "move","resize" or "new-size" (creating new events) | 
| e | Event | a native event object | 
scheduler.attachEvent("onEventDrag", function (id, mode, e){
    //any custom logic here
});
Modes description: