Bug 13525 - Date sorting on accounts (fines) tab doesn't work correctly

Bug 13525 - Date sorting on accounts (fines) tab doesn't work correctly

Date sorting of charges under Patron -> Fines -> Account is done based
on formatted dates, so sorting is broken depending on your dateformat
system preference. This patch implements the standard "title-string"
date sorting method.

To test, apply the patch and view the Account tab. Test sorting of
charges under various settings of the dateformat system preference. Date
sorting should work correctly in all cases.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Works as described and fixes sorting problem.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>