fixing not found error

[rettinghaus]

adds a function to return the correct GND-IDN for a processes record.
fixes #21

NB: maybe another place for that addition is better, as it also should do the trick for persons?

[rettinghaus]

pinging @ukretschmer

[ukretschmer]

Thnx for pinging @rettinghaus . Two things to think of:

1. As I see now, you are doing e new request for each result. Is there really no other way? If we got 10 results, this function will call the details of every result in a single request :/
2. Yes, there should be a better place for the function. Maybe we should provide a small "library" with viaf-specific functions for those using viaf as search interface, also for persons, etc.