For the definition of working/weekend days, ODFF1.2 uses 0..6
for Sunday..Saturday. NETWORKDAYS used ISO ordering (Monday..Sunday),
but now complies with ODFF1.2.

Change-Id: I169433adfac5d66af979181c328658040d7ab77f
Reviewed-on: https://gerrit.libreoffice.org/26246Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>