Bug 19365: Index authority fields as phrases

Followup change to the mappings syntax from bug 19893. Indexing as phrases allows to properly search for matching headings comprised of multiple subfields (e.g. author name with year of birth).

Sponsored-by: National Library of Finland
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>

18.11.x