Fix use of mappings from Wikidata

[nichtich]

This requires #136 and #46 which includes heavier cleanup at several places. Try

• https://gbv.github.io/cocoda/dev/?fromScheme=http%3A%2F%2Fbartoc.org%2Fen%2Fnode%2F745&toScheme=http%3A%2F%2Fbartoc.org%2Fen%2Fnode%2F1940&from=http%3A%2F%2Furi.gbv.de%2Fterminology%2Fbk%2F08&to=http%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ5891

In the Mapping Browser

• "CA - CK" is not highlighted because our current RVK in JSKOS uses URIs without _ around -. This is only a problem for notations which include - (see [another working example])(https://gbv.github.io/cocoda/dev/?fromScheme=http%3A%2F%2Fbartoc.org%2Fen%2Fnode%2F1940&from=http%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ156864)
• clicking "08" leads to an error because fromScheme has a different URI for BK and because the same concept is used at both sides (from and to)