title: Lithium: Remove related documents in a remove-Filter of a model
body: <p>I have a Games model which hasMany Avatars and Agents. When i remove the game, i want to clean up all the remaining data, so i also want to remove all Avatars and Agents with the corresponding <code>game_id</code>:</p>
  
  <pre><code>namespace app\models;
  
  use app\models\Avatars;
  use app\models\Agents;
  
  class Games extends \lithium\data\Model
  {
      public static function __init($options = array()) {
          parent::__init($options);
          $self = static::_instance(__CLASS__);
  
          Games::applyFilter('remove', function($self, $params, $chain) {
  
              $conditions = array( 'game_id' =&gt; $params['conditions']['_id'] );
  
              $message = new \app\extensions\helper\Message();
              $debugString = var_export($conditions, true);
              $message-&gt;addDebugMessage("params:{$debugString}");
              //Output: 
              //params:array ( 'game_id' =&gt; '4f301f69a170c8cf52000002', )
  
  
              if(!Agents::remove($conditions)) { $message-&gt;addErrorMessage('Es konnten nicht alle Agents geloescht werden.'); };
              if(!Avatars::remove($conditions)) { $message-&gt;addErrorMessage('Es konnten nicht alle Avatare geloescht werden.'); };
  
              return $chain-&gt;next($self, $params, $chain);
          });
  
      }
  }
  </code></pre>
  
  <p>Though the game gets removed, agents and avatars remain in the MongoDB.
  Does someone have a hint on this?</p>
  
  <p>Example of agent in db</p>
  
  <pre><code>&gt;db.agents.find()
  { "_id" : ObjectId("4f301f71a170c8391f000000"), "game_id" : ObjectId("4f301f69a170c8cf52000002"), "type" : "army", "subtype" : "deer", "units" : 5, "xPos" : 5, "yPos" : 5 }
  </code></pre>