example_headnodes directory to create a pxe machine with vagrant

the important puppet config file is manifests/site.pp. The manifests/templates directory contains the files copied into the correct locations to specify service config stuff.
I'm not 100% sure we want this in all cases. I'd at least put a comment here that says if you didn't want this you could hook a suitably secured headnode up to a network that customers have access to. This may still make sense in some cases, but originally it was a hack to get around the lack of public networks.