Bug 27926: Add 'title-string' for dates on circ-patron-results

Bug 27926: Add 'title-string' for dates on circ-patron-results

This patch adds the title string sorting for the data of birth field in
the circulation patron results table.  This has the side effect of
adding a tooltip that displays the date of birth in ISO format, so I'm
not entirely sure it's the right approach.

Test plan
1/ Set your date format preferences to British English (dd-mm-yyyy)
2/ Do a search that will yield multiple patrons via "Check out"
3/ Try sorting on date of birth and not the order is incorrect.
4/ Apply the patch
5/ Refresh the page and try sorting on date again
6/ The order should now be correct
7/ Signoff

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>