How to change public folder's location?

[Onezille]

Id like to move all leantime folders in private folder and only serve the content of leantime's public folder.
Folder structure should be like this (I'm using ISPConfig for servers):

private/
-- app/
-- bin/
-- config/...

web/ (served to internet)
-- css/
-- fonts/
-- images/...
-- index.php
-- download.php...

I managed to get it work by editing index.php etc files and some core files. But those changes get lost when updating.

Is there official way of doing it?