Rol for DNS infrastructure

For our DNS zones management, till now we use and contributed to systemli.bind9 role. Recently, with udelarinterior.bind9_cluster I tried a more efficient way to manage a set of DNS nameserves which are primary and secondaries of eachother, for some set of zones.

The migration fof our roles to collections is an opportunity to merge these two roles in a single one, with their API variables designed to coherently manage a whole cloud infrastructure, not server by server, letting the user of the role ensure the coherence among a related set of hosts.

Eventually, I'll try to code an important missing automatism: infering the NS records of the zone from BIND primary and secundaries servers.