Create a stand-alone validator for user_config.yaml

Server hardware often takes a long time to boot, so using a bare metal target to find syntax errors after booting off of DVD virtual media is extremely non-optimal. This story is to enable use of the validation code already in TA to check a user_config.yaml on the author's local machine prior to initiating a bare metal installation.

At a minimum the validator should support manual use and use as a Git pre-commit hook.