Database tab in admin panel

The idea was to *not* display the database tab in admin panel, if the user has no permissions.

One problem was, that a fresh install did not allow the admin user to see it, because the visibility of the tab is restricted to the "show sensitive data" log setting (which needs to be fixed). @Severin: Could you take care of that? I do not know the permission system yet.
Look out for @FIXME in ki_adminpane/init.php