Rename ol.Observable#dispatchChangeEvent() to #changed()

Since dispatchChangeEvent does not only dispatch a change event, but
also increases the revision counter, the method name should reflect
this.

src/ol/source/tilevectorsource.js

@@ -223,7 +223,7 @@ ol.source.TileVector.prototype.removeFeature = goog.abstractMethod;
  */
 ol.source.TileVector.prototype.setTileUrlFunction = function(tileUrlFunction) {
   this.tileUrlFunction_ = tileUrlFunction;
-  this.dispatchChangeEvent();
+  this.changed();
 };