BibField: new producer section added to config
- New producer section inside the configuration file that allows to produce different low level outputs for a given field.
- First release of two producers, one for marc and one for dublin core.
- New functions guess_legacy_field_names that, using the legacy rules from the configuration files try to find which is the field name for a given tag from a given master format.
- Better legacy export as marc that uses the new producer capability.
Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>
Co-authored-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>