Change pithos sharing to work with account uuids
Migrate username to uuid in pithos permissions
Fix negative population in statistics table
Provide error feedback during pithos database path migration to container uuid instead of email
Update Astakos API to provider calls for retrieving uuid from the username and vice versa, extend astakos client library (snf-common) and update pithos to use uuids instead of email for account identification
Fix code formatting to conform to the PEP 8 style guide
fix nodes latest_version revision
Refs: #2675
Introduce alembic