Show all levels of documents in Phriction

It is useful to be able to see all levels of documents in the Phriction document hierarchy, instead of just 2 levels. Organization is important, and so is being able to see ALL documents on one page - the Phriction index page (/).

NOTE: I removed lines 387 to 399 ("Fill in any missing children.") because I couldn't figure out why it was there, and it was adding in the grandchildren as children. As far as I can tell, all it does is re-add the grandchildren that were removed on [line 378](https://github.com/firejdl/phabricator/blob/571866ebf5cc03e221a1bef7e20dda9a60f60c51/src/applications/phriction/controller/PhrictionDocumentController.php#L378). I can add it back in if it is needed for something that I'm not seeing, but the issue of showing grandchildren as children will need to be addressed as well.