Specification for Dnsmasq DHCPv6

Blueprint dnsmasq-ipv6-dhcpv6-stateless
Blueprint dnsmasq-ipv6-dhcpv6-stateful

Change-Id: I4f3c15d1d43a27dd0e609107844d4715d39967e4
Merge "Specification for Dnsmasq DHCPv6"