Hook up archive upload related stats counters.

I'm not sure about this. As both revision and key are optional, we are left with
a situation where we can't know whether the 4th part of the key is a revision
number or a user. It seems a bit odd that user isn't before the charm name
actually. I wonder what the motivation for that was - it means that ~rogpeppe/precise/wordpress
counts towards global wordpress stats, AFAICS. Let's discuss this.