Add random cover to start page

[acka47]

@jschnasse proposed to add a random book cover to the start page analogous to the random organization at https://lobid.org/organisations (see hbz/lobid-organisations#321).

There are different source to get book/journal covers:

• Open Library book covers API: https://openlibrary.org/dev/docs/api/covers (short on book covers for resources in German)
• Book cover API by the GBV: https://verbundwiki.gbv.de/display/VZG/Buchcover
• Also, 128 resources with a ZDB ID have an image in wikidata: http://tinyurl.com/kjfc9qa
• On wikidata, > 2000 resources with ISBN10/13 have an image linked to them: http://tinyurl.com/lrwhh8l

Furthermore, there are different sources to get album and DVD covers:

• http://www.freedb.org (you need a disk id (see https://en.wikipedia.org/wiki/CDDB#Example_calculation_of_a_CDDB1_.28FreeDB.29_disc_ID) to request information)
• https://musicbrainz.org/
• https://www.themoviedb.org/ & http://www.omdbapi.com/ for movie posters & probably also wikidata

Generally, I think we should first add a link to covers to our data (as others would perhaps like to use it as well) and then we could show a random picture on the start page.

[dr0i]

As a low hanging fruit I propose to use http://lobid.org/download/dumps/DE-605/enrich/2de-dbpedia.ttl . There are ~6000 links to german dbpedia. These links are conservatively created to avoid false hits. I assume there are some hundreds of covers, e.g. http://de.dbpedia.org/resource/Der_Name_der_Rose.

edit: hm, seems covers are not in the data, see also http://dbpedia.org/resource/The_Name_of_the_Rose (which has the cover in the info box in the wikipedia https://en.wikipedia.org/wiki/The_Name_of_the_Rose)