Fixed bug with unused grid route parameters

I dont know for what the grid need a route if not for this... :+1: 

Example why I need that:

**Controller**
```php
<?php
use APY\DataGridBundle\Grid\Action\RowAction;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Acme\DemoBundle\Entity\Company;
use Acme\DemoBundle\Entity\Branch;
/**
 * Class CompanyBranchController
 * @Route("/{company}/branch", requirements={"company" = "\d+"})
 * @ParamConverter("item", class="AcmeDemoBundle:Company", options={"id"="company"})
 */
class CompanyBranchController extends Controller
{
	/**
	 * @Route("/list", name="route_for_list")
	 * @Template
	 */
	public function listAction(Company $item = null)
	{
		$source = new Entity('AcmeDemoBundle:Company');

		/** @var $grid \APY\DataGridBundle\Grid\Grid */
		$grid = $this->get('grid');
		$grid->setSource($source);
		$grid->setRouteParameter('company', $item instanceof Company ? $item->getId() : 0);
		
		// Specify route parameters for the edit action
		$rowAction2 = new RowAction('Edit', 'route_to_edit');
		$rowAction2->setRouteParameters(array('id', 'company.id'));
		$rowAction2->setRouteParametersMapping(array('company.id' => 'company'));
		$grid->addRowAction($rowAction2);
	}
```

The examples throw...

```
An exception has been thrown during the rendering of a template
("Parameter "company" for route "route_for_list" must match "\d+" ("" given) to generate a corresponding URL.")
```

If i use the patch it would work without this:

```php
		$rowAction2->setRouteParameters(array('id', 'company.id'));
		$rowAction2->setRouteParametersMapping(array('company.id' => 'company'));
```

Then your grid uses the default "id" field for the edit route and the company field for the branches.

**Example usage:**

```php
...
	/**
	 * @Route("/edit/{id}", name="route_to_edit")
	 * @Template
	 */
	public function editAction($id)
	{
		/** @var $company Company */
		$company = $this->getRequest()->get('company');

		/** @var $branch Branch */
		$branch = $this->getDoctrine()->getRepository('AcmeDemoBundle:CompanyBranch')->find($id);
		...
	}
...
```

**php app/console router:debug**

```
route_for_list    ANY      ANY    ANY  /{company}/branch/list
route_to_edit     ANY      ANY    ANY  /{company}/branch/edit/{id}
```

Thank's.