Thesaurus picker for dct:type

[joachimnielandt]

The following issue is a result of a check performed by @CMath04 during the last sprint. To be concluded / fixed, I'm creating a relevant issue to track progress whenever we can pick this up.

License dct:type should be a thesaurus picker. At the moment, it is not recognized as such and clicking the corresponding + button results in a new, nested, dct:LicenseDocument (infinitly nestable)