Several minor changes

Several minor changes

* change visible fields in user profile page
* change visible fields in user modification administrator page
* enable administrator to update user quota
* read default user level from settings
* show sent invitations and status in user invite page
* if no next request parameter after login redirect to index page
* after successful login set cookie (read cookie name & domain from settings)
* delete cookie in logout
* rename `dummy` target to `redirect` and change its functionality