Make $pageController->render() a little more powerful.

[aembler]

Right now it just dumps the current page and instead renders a new one in its place, running the new view method and everything. Instead, we bring back 5.6 behavior. This means that

$this->render('/path/to/whatever');

will actually grab this view at the current path (including looking in the package directory if the current page is a packaged page) and use that view as the view instead of the current pages view. This will be similar to $renderOverride was in 5.6 (but more elegant.)