Upload usage data to Google Docs

The all_certificates method is a quite long running task, so probably not that sensible to generate this in the frontend. I've moved the stats jobs mentioned in https://github.com/theodi/shared/issues/216 (apart from 3), which I haven't done yet) to a DelayedJob task which runs on a weekly basis, and uploads the files to Google Docs. The added advantage of this, is we have an archive of previous stuff too, plus @sumikasan doesn't have to manaually get the stats each time.

Need to add an extra ENV variable to Chef, but this is good to go once I've done that.