title: Add events to event source dynamically
body: <p>Thanks for the project ! Really nice !</p>
  
  <p>I am currently trying to upgrade full-calendar from v1 to v2.
  I fixed all the majors issues thanks to the Upgrading to v2 page documentation.</p>
  
  <p>I am now stuck on a conceptual problem...</p>
  
  <p>My calendar displays events by users. 
  Each user is represented by a source of events. 
  Source of events are basically an array of events.
  When I add an event for a user, I want it to be added to the user's source of events in a dynamic way. This way I always have a complete matching between sources and displayed events on calendar.</p>
  
  <p>I succeeded to implement this use case in v1 as follows :</p>
  
  <pre><code>private void addEventToSource(Event event) {
    // get user 
    String userId = event.getUserId();
    // get source for user (sources is a map user -&gt; JsonObject)
    JSONObject source = sources.get(userId);
    // get the list of events
    JSONArray array = (JSONArray)source.get("events");
    // add event at the end of the list
    array.set(array.size(), createJsonEvent(event));
    // refetch events from all sources
    refetchEvents();
  </code></pre>
  
  <p>}</p>
  
  <p>This code works well thanks to the fact that the user's source is previously known by full-calendar js :</p>
  
  <pre><code>private static native void addSource(String calendarId, JavaScriptObject source) /*-{
    $wnd.jQuery("#"+calendarId).fullCalendar('addEventSource', source);
  </code></pre>
  
  <p>}-*/;</p>
  
  <p>Internally, all my updates are done on the source object through JSON manipulations. When I refetch the events, all my users' sources are up to date and well displayed on the calendar.</p>
  
  <p>However, this code does not work on v2. It seems that the source I send to full calendar is different than the one internally used to display events. All my updates on the source are not applied to the internal data, and so not visible on the calendar.</p>
  
  <p>Is there a way to get the inner sources of events used ?
  Any idea to implement such a use case ? Maybe I missed something...
  Thanks in advance !</p>
  
  <p>Julien </p>