qBittorrent should support ipv6

libtorrent supports ipv6. Hence, qBittorrent code shouldn't be limited to ipv4. I think we only use ips in our IPFilter but we should check at other places too. Anyway, IPFilter must be updated because it is ipv4 only at the moment. libtorrent use asio address format : see asio address_v4 and address_v6. We must use those types too. User should be able to add ipv6 ranges of IPs in the filter and we should be able to parse filter.dat files with ipv6 adress ranges.