add register-node and register-server support

register-server, to be executed locally on a chef server, will register chef server's /etc/chef/validation.pem key so that a client can pull it and authenticate with that server.

register-node, to be executed locally on a unregistered chef client, will register the local node to the identified chef server
Merge branch 'master' of github.com:rerun-modules/chef-solo