UrlGenerator to accept extra parameters

Symfony2's UrlGenerator accepts extra parameters and extra params are added as query string to the URL. So should we.

### Example:
routes.php:
```php
Route::get('testroute/{id}', array('as'=>'testroute',function($id)
{
    return 'This is :'.$id . 
        'And this is QS : '. $_SERVER['QUERY_STRING'];
}));
```
the only parameter is {id}. but if we post 2 parameters to url builder like this:
```php
return URL::route('testroute',array('id'=>999,'diren'=>'geziparki'));
```
generated URL will be:
`/testroute/999?diren=geziparki`

This is so useful with strict route definitions like in `Route::resource` controllers.