Create split out neutron networks via Heat.

Create split out neutron networks via Heat.

This patch adds a new abstraction for network creation
within Heat. This (optional) set of templates may be disabled
if you wish to create Neutron networks for the undercloud
via Heat templates... instead of using os-cloud-config
JSON to do so. Creating networks with Heat has the benefit
of being parameter driven so that users can quickly
enable networks using the resource registry and parameters.

There are 5 networks to start with which are roughly modeled
around networks an Overcloud user might want to use to isolate
their traffic. The intent is to make these opt-in and
configurable for end users.

The networks.yaml template can be used to create all of the
networks using parameters in the resource registry.

Change-Id: I5f2b3356378eb263d90d428cc83c7f5b141957e1