Bug 15400: (follow-up) Adding age to check out search dropdown

Bug 15400: (follow-up) Adding age to check out search dropdown

Confirm age shows in the suggestions dropdown when using the checkout
search in header (if user set DOB).
Confirm 'Age unknown' shows if no DOB set.

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>