Fedora, UUIDs, and user tracking

This is something we've been talking about on the list. I think right now we're looking at "first week", "after the first week", "first week after a distro-upgrade", carrying the contents of /etc/os-release which should give us much of what we really need:
* Metrics on how many systems are short-lived (e.g. testing environments) vs long-lived and/or upgraded vs. freshly installed.
* Rough metrics on user counts that are a better approximation than the current guesses at the mirrorlist hits.