Necessary changes for Wikidata write access support

[stefandesu]

Write access via wikidata-jskos is ready to be added. It works out of the box, but there are some necessary adjustments needed in Cocoda before shipping the feature:

• Adjust config
• Wikidata mappings don't include a creator. Because of that, editing a mapping will always show that it has changed (because it assumes the new creator). We need some kind of exception for that.
• Wikidata only allows mappings from Wikidata to something else (and also only to supported schemes). We should at least make sure that there is an option saying that only WD -> X mappings are supported. Even better would be to load the list of supported schemes and check against that.
• wikidata-jskos will return a new config key config.auth.identityProviders which is a list of possible identity providers it can use (in this case only "wikidata"). Cocoda should take this into account when checking whether the user is authorized for Wikidata.
• Bug: If a Wikidata mapping exists between the currently selected concepts, it is somehow shown twice (seems to be a Cocoda issue, not wikidata-jskos). Edit: It's a bug in wikidata-jskos related to having both from and to as parameters. Will be fixed there.

[stefandesu]

Implemented on a separate branch, soon to be merged into dev.