shrinking EP DB
DB was growing fast since pool is included every 100 revisions https://github.com/ether/etherpad-lite/commit/d4fcc23fb382aba7c65bc7e5376d2ab9fc6e2f8a - we have patched that meanwhile, see https://github.com/ether/etherpad-lite/issues/4642
We are going to analyse if the DB can be shrinked in some way and if we can use EP without patch again.
- check if images are stored in apools
- check if we can delete the pool at each 100 revision