Enable DNS for services

Open issues as of 11/15

Needs e2e testing

Question: Can services exist above "default"?  I.e. do we need to search (domain) and (ns).(domain) or just (ns).(domain) ?

Should default.(domain) be in everyone's search list?

TODO: plumb DNS to minion's resolv.conf for use from host

TODO: fix portals for UDP from host (works from a container)
 - source address is wrong on response from host:
   OUTPUT -> -A KUBE-PROXY-LOCAL -d 10.0.0.10/32 -p udp -m comment --comment skydns -m udp --dport 53 -j DNAT --to-destination 10.240.239.33:41504

TODO: Need a specific version tag on the skydns, kube2sky, and etcd containers.

I would much rather name this "EnableClusterDNS" and default to true, but the way we do defaulting, I can not tell if the user set it to False or expected the default.

This exists primarily so that SkyDNS does not try to use itself for DNS lookups.  Maybe we don't NEED it (would have to try), but it feels scary to have this self-loop.