Sample environment generator

Sample environment generator

This is a tool to automate the generation of our sample environment
files.  It takes a yaml file as input, and based on the environments
defined in that file generates a number of sample environment files
from the parameters in the Heat templates.  A tox genconfig target
is added that mirrors how the other OpenStack services generate
their sample config files.

A description of the available options for the input file is
provided in a README file in the sample-env-generator directory.

In this commit only a single sample config is provided as a basic
example of how the tool works, but subsequent commits will add
more generated sample configs.

Change-Id: I855f33a61bba5337d844555a7c41b633b3327f7a
bp: environment-generator