Forward actions from VirtualPage to target controller

Fixes #1101 
I forgot about the ```::controller_for``` function! However, the controller would still need to be stored in a variable as it needs to limit ```allowedActions()``` by classname (unless you want an über long return line) e.g 
```php
$controller = ModelAsController::controller_for($this->CopyContentFrom());
return $controller->allowedActions(get_class($controller));
```
as opposed to:
```php
return ModelAsController::controller_for($this->CopyContentFrom())->allowedActions(get_class(ModelAsController::controller_for($this->CopyContentFrom())));