Remove inactive users handling in favor of "inactive user" module

Issue Summary

As I'm not sure about the scope of this project (created users are just temporary or not) I would suggest to avoid handling inactivity in this module. Users to be removed due to their inactivity period would be managed with the "inactive_user" ( http://drupal.org/project/inactive_user ) module as it provides more facilities to handled that situation.

I propose to remove the inactive handling in this module for future versions. (Drupal 5 version of the inactive_user is available although it's not published in the project module).