fixes #1111 - add support for IPv6 addresses (tracking, anonymization, and exclusion)

fixes #2095 - add new anonymization hook (pre-heuristics)
fixes #2055 - optional IP filter when multiple proxies present
fixes #1775 - SitesManager: supports CIDR notation for IP exclusion

Notes:
 * Installer no longer checks for IPv6, so the related messages should be deleted from translations
 * IPv4 mapped addresses (e.g., ::ffff:127.0.0.1) are no longer re-mapped into IPv4 space
 * users who to query IP addresses from MySQL directly, can use the following SQL, but inet_ntoa() is limited to IPv4 addresses:
{{{
select inet_ntoa(conv(hex(location_ip), 16, 10)) from piwik_log_visit;
}}}
 * Windows: IPv6 inet_pton()/inet_ntop() not supported until php 5.3; see #2351


git-svn-id: http://dev.piwik.org/svn/trunk@4533 59fd770c-687e-43c8-a1e3-f5a4ff64c105