Add labels to ID fields

[acka47]

For example http://test.lobid.org/authorities/118506560.

Currently looks like:

{
"professionOrOccupation": [
  "http://d-nb.info/gnd/4131406-2",
  "http://d-nb.info/gnd/4012434-4"
  ]
}

With added labels:

{
   "professionOrOccupation":[
      {
         "id":"http://d-nb.info/gnd/4131406-2",
         "preferredName":"Pianist"
      },
      {
         "id":"http://d-nb.info/gnd/4012434-4",
         "preferredName":"Dirigent"
      }
   ]
}

However, there are several other cases (e.g. placeOfDeath, relatedWork, familialRelationship) where we only have internal GND links without labels in the data. Thus, a general approach would probably make sense to automatically add a label for all URIs from the http://d-nb.info/gnd/ namespace. (If we implement a general approach, it should be possible to exclude some properties from this label enrichment, e.g. we might get problems with trying to fetch the label for deprecatedUri and also labels for sameAs links within GND aren't necessary I think.) What do you think, @fsteeg?

[fsteeg]

From the logic/implementation view this should work. We already get labels for GND URIs in the UI. We could use the previous index data when running a transformation. It would significantly increase processing runtime however, since we'd have to analyze every record for values to add, and issue multiple index requests for each record.

[fsteeg]

Full list of ID fields to add labels for (taken from #26):

• professionOrOccupation
• placeOfBusiness
• placeOfConferenceOrEvent
• firstAuthor (firstComposer etc.)
• geographicAreaCode (depends on Get GND vocabs for labels #17)
• gndSubjectCategory (depends on Get GND vocabs for labels #17)