Feature request: automated user registration

Please introduce a functionality allowing users to register and automate the process of registration.

Suggested way this could work:

1. The user click on the "Request an account" button
2. A form pops up prompting the user for an email and password
3. The user appears in the system as "requesting", with login == email
4. An email with an activation link is sent to the user
5. After the activation link is clicked the user gets an on-screen notification that his request will be reviewed
6. the status of the user changes to "pending"
7. A notification is sent to the admins (contact email) to review the user and assign a role
8. When a role is assigned, the user gets a notification that his account is set up

@piotr.gawron what do you think? We discussed this for a bit with @ewa.smula .

We could consider skipping steps 4-6 (activation link), but then there will be no control if the email is valid.