Cleanup old data
The tables have become rather huge and not all of it is relevant.
--- /var/lib/mysql/stats
8.9 GiB [##########] extensions.MYD
6.5 GiB [####### ] entities.MYD
3.5 GiB [### ] entities.MYI
2.6 GiB [## ] extensions.MYI
1.8 GiB [## ] stats.MYD