Provide copying sameAs authority info to local data set

[ukretschmer]

Currently the application supports getting authority IDs of one kind, depending on the configuration. It would be a nice feature, e.g. for persons load from GND, to be able to copy the already provided "sameAs" relations into local data.

[ukretschmer]

Possible implementation:

1. Provide a config option, e.g. config.api.${context}.storeSameAs (Boolean)
2. Add functionality somewhere around togglePreferred?

If an ID is set as preferred and storeSameAs is true copy sameAs from fetched object to local object. All storage handling would be done via events preferredReferenceChange, cardPreferredReferenceChange and mapPreferredReferenceChange