New IPv6 integration

git-svn-id: http://svn.luci.subsignal.org/luci/trunk@9636 ab181a69-ba2e-0410-a84d-ff88ab4c47bc
move dhcpv6 support into luci-proto-6x4, rename luci-proto-6x4 to luci-proto-ipv6

git-svn-id: http://svn.luci.subsignal.org/luci/trunk@9637 ab181a69-ba2e-0410-a84d-ff88ab4c47bc