Bug 8168: Fixing header of non CSV files for overdue notices

Bug 8168: Fixing header of non CSV files for overdue notices

This determines if the CSV header should be included or not and
then generates it as needed using the delimiter specified in the
delimiter system preference.

TEST PLAN
---------
1. make some overdues books
2. run the overdue notices script without the -csv
3. check emails notice csv header is in the email
4. apply the patch
5. run the overdue notice again
6. check email notice CSV header is absent

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: wajasu <matted-34813@mypacks.net>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>