Change self to static in findOne method in order to allow child class…

…es to override the find method and use that in the fineOne method

TRest/Models/Model.php

@@ -43,7 +43,7 @@ public function delete() {
      * @return Model
      */
     public static function findOne($id) {
-        return self::find()->findOne($id);
+        return static::find()->findOne($id);
     }
 
     public static function findOneByQuery($id, Query $query){