Support for controller instance method filters using @filter syntax, proposal #2432

Makes it very fast and easy to use instance methods on your controller as filters. Helpful in cases where maybe you need to do a permission check (like checking if the logged in user actually owns the post they are trying to delete for example) on several actions, and you don't want to register a global filter since the functionality is localized to that controller. A lot cleaner than using closures.

```php
public function __construct()
{
    $this->beforeFilter('@hasPermission');
}

protected function hasPermission($route)
{   
    $id = $route->getParameter('id');

    if (! Auth::user()->ownsPost($id)) {
        return Response::make('You are not authorized', 401);
    }
}
```