Make several updates to the AccountStatusNotificationType class:

- Use integers rather than strings as the identifiers for the notification
  types, which will make them easier to compare as well as easier to
  internationalize.
- Change the ACCOUNT_REQUIRES_ADMIN_UNLOCK type to the simpler and more
  consistent ACCOUNT_PERMANENTLY_LOCKED type.
- Change the PASSWORD_RESET_BY_ADMINISTRATOR type to the more compact
  PASSWORD_RESET type.
- Add ACCOUNT_RESET_LOCKED and ACCOUNT_EXPIRED types.