[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, this part would be better if the :required => true flag provided a useful error message.

I had to workaround that by raising a useful error message if the reference is nil or empty String.