BibIndex: new tag for address field

* Associates the 'address' field to a single '371__%' tag instead of many
  '371__a', '371__b', '371__c', ... tags
* Keeps other tags associated with the 'address' field: '110__a', '10__b',
  '110__t', '110__u', '410__g'

Signed-off-by: Federico Poli <federico.poli@cern.ch>