Setting the open_basedir like this doesn't work in DSM5.0. `php_admin_value` is not allowed in .conf files. Anyway, added a step in the wizard to manually add the path to the open_basedir to mitigate this, which works for DSM4 and DSM5.

With MantisBT, I used an if-statement for DSM4 for the .conf file, but I'm not liking that either (apart from the fact that it seemed to work without it on both DSM4 and DSM5, hence the comment in the code)