Bug 22875: Document verbose option in import_patrons

Bug 22875: Document verbose option in import_patrons

Docs did not state that verbose can be repeated or that you
need more than 1 repetition to see lines that have failed

To test:
- Run ./import_patrons.pl -h
- Verify the additional documentation for -v is shown.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit d9248c8802c4009ca99209da549447d13d6f686f)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>