generate man pages for kubectl using the cobra.Command information.
This will directly create files in (by default) docs/man/man1/ called
kubectl*.1. Each child verb/cobra command will gets its own man page.
--sync_nodes=false gives user flexibility to add/remove nodes in the
cluster using REST api/kubectl cli and at the same time can use
cloud provider for other resources like persistent disks, etc.
Part of #108.
Also:
* Added hyperkube cmd (not built by default yet).
* Added version support to hyperkube
* Remove health_check_minions flag from apiserver as it is no longer used with #3733
