Bug 7818: add index_data_field option to DOM indexing repertoire
Adds a new kohaidx:index_data_field index definition type which
indexes all of the subfields of a MARC data field as a single
phrase, separating the contents of each with a space.
Signed-off-by: Galen Charlton <gmc@esilibrary.com> Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com> Signed-off-by: Paul Poulain <paul.poulain@biblibre.com> Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>