Closes #275

See merge request !1492

Closes #276

See merge request !1507

See merge request !1490

See merge request !1502

See merge request !1500

See merge request !1496

Closes #270

See merge request !1495

See merge request !1494

Remove the property type added as a comment to the Conf.py files. It was
entirely cosmetic and often wrong (e.g. maps were annotated as `# list`).

Relates to issue #219.

- replace `.format` with f-strings
- replace `setattr` with direct `_properties` access in `merge`

More precisely, json data come from the JSONSink and this produces a list of non ordered items, one may call it a set.
Unfortunately JSON does not have such a concept so an ordered list is produced and the validator was naturally checking that the order was correct

See merge request !1483

it's not used for Python descriptor protocol and confuses people

See merge request !1415