Many smaller fixes for migration. Basic migration test.

.vscode/launch.json

nomad/api/app.py

nomad/api/repo.py

nomad/api/upload.py

nomad/client/misc.py

nomad/files.py

nomad/migration.py

nomad/processing/data.py

tests/bravado_flaks.py

tests/data/migration/baseline/upload/1/template.json

tests/data/migration/baseline/upload/2/template.json

tests/test_client.py

tests/test_migration.py