The RepositoryActionCount table can have entries added while a repository deletion is in progress. We now perform the repository deletion under a transaction and explicitly test for RAC entries in the deletion unit test (which doesn't test interleaving, but it was missing this check).
Fixes#494
Implement the minimal changes to the local filesystem storage driver and feed them through the distributed storage driver.
Create a digest package which contains digest_tools and checksums.
Fix the tests to use the new v1 endpoint locations.
Fix repository.delete_instance to properly filter the generated queries to avoid most subquery deletes, but still generate them when not explicitly filtered.
