Add script to cleanup users that never verified their e-mail or logged in

[dboehmer]

On Coocook.org we have hundreds of autocreated users. Some of them never verified their e-mail address.

The script should offer

• remove users who failed to verify their e-mail address longer than n days
• remove users who never logged in and exist since n days

[dboehmer]

Done with cc9f493