Primo: make data extraction slightly more general

I don't think that is a good idea. The PNX section `search` is for the retrieval and therefore contains a lot of different name forms normal. For example in our catalogue (MAN_ALEPH001271912), we have over 100 different name variants for "Goethe" e.g. "Koet'e, Yohan Polp'ŭgang p'on" and they are all saved in `<creatorcontrib>` fields in the `<search>` section of the PNX. They should definitely not imported as different authors.