Deployed server bootstrap via Heat

Deployed server bootstrap via Heat

Adds an environment file, template, and script that can be used to do
initial bootstrapping of deployed servers during NodeExtraConfig. It is
meant to install and configure the initial dependencies needed to apply
the rest of the OpenStack configuration via Heat.

Enabling yum repos and installing the initial python-heat-agent package
would still have to be manual steps when using this environment. But the
goal is to keep those manual steps to a minimum and automate as much as
possible in deployed-server-bootstrap.sh.

Along with setting EnablePackageInstall: True, this could eventually
replace bootstrap-overcloud-full.sh from tripleo-ci.

Partially-implements: blueprint split-stack-software-configuration
Change-Id: I6be94604a46382e6288df1b36b9de8fab58696cc