[WIP] Use trollop option parsing for git reference instead of VERSION file

The VERSION file path as part of the nightly build scripts was not reliable.

Additionally, it feels ugly that the build code used to generate the kickstarts for the appliances needs to have access to the VERSION file from the desired branch/tag/reference.
Yeah, the case statement in build.rb needs to be removed but not in this PR.  The entails untangling the meaning of "nightly" to be something more obvious.