Prefixes defined in id_ranges.toml are ignored

[dalito]

Observed in v0.8.8 while working on #253: The prefixes are read in correctly from the config file but are later overwritten later by the default rdflib prefixes. As a result, the code always writes IRIs to Excel (for the voc4cat vocabulary). But even now in 0.8.x it should write CURIEs instead of IRIs, but no one noticed.

Instead of just fixing this, we will also make the prefixes sheet read only in v0.9.0. Keeping id editable makes no sense, since

• all user-made additions will always be lost in the xlsx -> rdf -> xlsx conversion,
• the ´xlsx´ that is downloaded to make new contribution has to be always be the same for all users.

The better way to define additional prefixes is to add them to idranges.toml in a PR to the vocabulary repository. This way they are shared with all users and survive all conversions.

This will be part of 0.9.0. The idea to make the prefixes sheet read-only is coming from the ideas collection for 1.0.0 (#124).