this allows to build the test db on the fly:
- make it inherit from SingleDbTestFixture, so we can
- move sql files in swh/storage/sql/
- get rid og the setUpClass static method to reuse the one from SingleDbTestFixture,
- apply the required modifications to tests based on this StorageTestFixture.
Warnings:
- this requires D538,
- this will break tests in swh-vault.
Also add README.md to the MANIFEST.in file so it does not require
a too recent setuptool.
kill sql/db-init in favor of swh-core's new swh-db-init tool
sql: adapt Makefile for sql file renames and make it pifpaf compliant
ie. delete stamps when executed via pifpaf for the db setup.