Fix typo in filter.inc. Fixes #3028.

Due to the typo, FilterIfList never got a 'track6-interface' entry,
which in turn prevented the DHCP6-related pass rules from being
generated for the LAN interface.
touch up text
fix description
Fix #3079, add a section for DHCPv6 Server backup
Fix the "use ICMP" function for traceroute.
Add independent logging choices to disable logging of bogon network rules and private network rules. Add upgrade code to obey the existing behavior for users (if default block logging was disabled, so is bogon/private rule blocking). Also add a checkbox to disable the lighttpd log for people who don't want their system log spammed by lighty.
Use empty to cover all needed cases as suggested on #3062. Suggested from pull request #698
Implement proper releasing of pipes allocated based on CPzone. Keep track of which zone a pipe is and release those pipes during disabling/deleting of zone. Ticket #3062, Pull request #698
Don't automatically add hidden rules to pass all IPv6 traffic to/from delegated prefixes. Default IPv6 from LAN -> any rule covers outbound properly as-is, and WAN rules shouldn't pass in that permissively. Also the prefix length calculation was off and the LAN rule(s) would be too permissive anyhow.