Anonymize IP exceptions

I added two options to the Privacy settings page:

* Allow using non-anonymized IP address to determine the visitor's location
* Allow using non-anonymized IP address to determine the visitor's ISP

When these are activated, the visitor's original IP address is used to determine location and/or ISP, in order to get a more accurate value.

The IP address saved in the `log_visit` table will honor the `ip_address_mask_length` setting.