Enhance interlinking of the three lobid services

[acka47]

This is a superissue for different tasks we partly already have tickets for:

• Add links from GND entitites to lobid-resources: https://github.com/hbz/lobid-gnd/issues/38
• Add GND links to lobid-organisations: https://github.com/hbz/lobid-organisations/issues/361
• Add search box in lobid-organisations for libraries we have holdings in lobid-resources: https://github.com/hbz/lobid-organisations/issues/397
• Furthermore, @dr0i recently suggested to link to lobid-gnd instead to the DNB catalog when in lobid-resources clicking on the link symbol besides a person, corporate body or subject heading.