Bug 11592: Updated License Text and use Modern::Perl

Bug 11592: Updated License Text and use Modern::Perl

Why not clean up the License Agreement stuff while the files
are being changed? Used the current one found at:
http://wiki.koha-community.org/wiki/Coding_Guidelines#Licence

Changed the strict and warning lines into just a Modern::Perl.

Signed-off-by: Robin Sheat <robin@catalyst.net.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>