Add config option 'groups_admin' to allow users to become dokuwiki admins by being in a list of django groups

Fix Plugin: Add missing semicolons to lang/en/settings.php

Make all django users member of dokuwiki group 'user', add options to make django admins and/or staff members of dokuwiki group 'admin'

Add new config option to add a logoff URI

Add correct php headers to all php files

Add config description strings