OS-438, IPv6 support for Infoblox

* In https://jira.inca.infoblox.com:8443/browse/OPENSTACK-438 you may grab shell script to test functionality.
* Currently we support only DUID-LL stateful IPv6 (https://tools.ietf.org/html/rfc3315#section-9.4), so to get IPv6 in stateful mode run dhclient -6 -D LL eth0

We can create mixed subnets in one network, both ipv4 and ipv6. So we should know where we must forward traffic from different subnets.

Regarding to new migration file, what do you think if me collect all our changes in DB, related to infoblox, and put them in one migration file?
It will simplify rebasing process,  because i beleve noone will have access to our development history and we will provide single commit to review in community. nad will be greate to have it as compact as possible.