Description:
------------
Creating a plugin from Yaf_Plugin_Abstract and registering it at the dispatcher, 
will not have the preResponse method executed.

Test script:
---------------
<?php 
$config = array(
	"application" => array(
		"directory" => realpath(dirname(__FILE__)),
		"dispatcher" => array(
			"catchException" => 0,
			"throwException" => 1,
		),
        "modules" => "module",
	),
);

class ControllerController extends Yaf_Controller_Abstract {
    public function indexAction() {
        Yaf_Dispatcher::getInstance()->disableView();
        echo 'indexAction in Controller';
    }
}

class UserPlugin extends Yaf_Plugin_Abstract{
    public function preResponse($request, $response) {
		echo "preResponse in Plugin".PHP_EOL;
	}
}

$app = new Yaf_Application($config);
$request = new Yaf_Request_Http("/module/controller/index");
$dispatcher = $app->getDispatcher();
$user = new UserPlugin();
$dispatcher->registerPlugin($user);
try {
  $dispatcher->returnResponse(true)->dispatch($request);
} catch (Yaf_Exception $e) {
  echo $e->getMessage(), "\n";
}
?>

Expected result:
----------------
preResponse in Plugin
indexAction in Controller

Actual result:
--------------
indexAction in Controller