In-app-search for wikidata IDs

[hejjoe]

When adding memorials, graves or similar items it could be very helpful to look up the right wikidata IDs for keys like subject:wikidata, buried:wikidata or artist:wikidata within the app. Otherwise the IDs has to be search in a separate browser app. This in-app search might be done with the wikidata REST api and/or wikidata api tools.