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Refs: #1993

Refs: #1993

* 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

-incorporate CsrfViewMiddleware
-change tamplates to render forms
-change email template location
-api.activate() returns only information about token
- In prepare_response, instead of setting the cookie, log the user in
- use django.contrib.auth.views for reseting and changing user password

Ref: #1874

- extend django user model
- pass template_name and extra_context in views
- incorporate context processors
- use different backends for invitations and simple workflow

Refs: #1823