Set proper extractedBy field value indicating its origin for Grobid-based processing

[marekhorst]

This is a #1560 follow-up. Grobid-based metadata extraction needs to set an appropriate extractedBy field value.

Important remark: exception handling for Grobid-based metadata extraction results in setting an empty record. It needs to be supplemented with a proper extractedBy value as well. Current implementation needs to be refactored because currently exception handling is shared for both and results in producing empty record with extractedBy value set to CERMINE.