Better document which events are fired

The map does not fire ol.render.Event#render. Change events are
now only listed for classes that fire them, and a description
about when they are fired is added.

src/ol/observable.js

@@ -31,8 +31,7 @@ goog.inherits(ol.Observable, goog.events.EventTarget);
 
 
 /**
- * Dispatches a `change` event. Register a listener for this event to get
- * notified of changes.
+ * Dispatches a `change` event.
  * @fires change
  * @todo api
  */