Feature: Multi-site/Multi-cluster/Multi-config via templating and site-specific values (instructions reusability)

[ahuffman]

As a user, I have several environments and/or configurations to manage. I often have a set of values that are common to all the differing configurations, but I also have some values that need to be overridden with alternate values for specific environments.

I would like to be able to pass in a named directory, where the directory is the name of my site, which contains a collection of yaml files that apply to that site, and many others as well. I would also like to pass in a set of common values, that the site specific values will get merged over to perform overrides when templating.

Order of Operations:

1. Common Values are read in
2. Site Values are read in
3. Instructions are templated based on configured templating language
4. Repeat for each add'l multi config values

These multi-config values should be passed in with a -m /path/to/my/site/dev or --multi-config. This option can be passed 1 or many times.

Additionally, I would like to have a parent directory containing several sub-directories that are named by their site/purpose, and all contain yaml files which are values for templating. I would like to also be able to pass them all in at once with -m or --multi-config.