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.

Addresses #1261.
// TODO: Move this default setting out of the validation function once there's a home for it.