Updates Pupetfile

Adds capability to ooverride settings by placing
a custom Puppetfile in the builder_overrides directory.

This allows us to trim this file down to the bare essentials
required to install base openstack.
Update vagrantfile

- for compat with vagrant V2
- to allow external nodes to be defined by vendors
Embed hiera into manifest

B/c otherwise you have to deal with another
directory. It's a lot of fuss for such a tiny
bit of config.
Ensure that override files are ignored

They are intended to be copied in after this repo
is cloned, but not commits into it.
Remove modules.list

We are not going to use it
Remove image building code
Ensure that dependencies are set up

So that Puppet packages will only be installed
after the apt source definitions are configured.