Automatically delete or disable sub users on deletion or disabling of the parent user

I think this is a good idea if this havent been done yet.

Here's patch that adds support for deleting subusers. I think it should be possible to also support disabling the subusers, and there should be some message about the deleted subusers.

Fixed whitespaces away.

Created patch with little different approach. Now we're deleting all subusers recursively. Still need to figure out if it's possible to get those duplicate messages away.

Instead of limiting the additional feature to only deletion, I would suggest to make it also possible to auto-disable subusers if the parent account has been disabled.