Configuration in YAML

These patches move configuration to /etc/foreman/puppet.yml. By moving the configuration into a settings file, we can use external_node.rb and
foreman-report as plain files and prepare it for proper packaging.

This is based on a patch by @frimik and replaces https://github.com/theforeman/puppet-foreman/pull/87 since I can no longer push to @oxilion.
all these foreman_* settings are wrong, in the config file they're just `:ssl_ca` etc.