Add API for more Data Modals

[nichtich]

In some cases the "Export JSKOS Data modal" contains API links. These links should include source name and/or URL, if available (e.g. "JSKOS Server" or "DANTE API"). If only a source is known but no full API URL, just show the name to allow looking up the main source of the data.

Example: GND concepts are loaded from https://lobid.org/gnd/