Redmine

This patch adds a new value for the --unknown-user option of the mail handler script.

When given, it will behave similar to --unknown-user=create, but the user account will not be automatically activated. Depending on the site configuration, either token activation or manual activation by administrator will be required. The purpose is to help keep spam level low on public projects.

The change is a bit involved as it required moving the registration logic from accounts controller to the User model.