Add download counts into elasticsearch

Total download counts are now in elasticsearch. Along with some changes to the integration that made things simpler. It will be possible to implement sorting and boosting on download counts.
I was following the lead set for updating the stats for a download. Stats are updated asynchronously, presumably because we don't want to hold up the charm download. As ES is updated from the stats it has to be done asynchronously too. If the update is asynchronous it may take a little while to occur.