Bug 7567: (code cleanup) update license and use Modern::Perl

Bug 7567: (code cleanup) update license and use Modern::Perl

Grabbed the current license from
  http://wiki.koha-community.org/wiki/Coding_Guidelines#Licence
and changed the use strict; use warnings; into a
use Modern::Perl instead.

TEST PLAN
---------
1) Log into staff client.
    - Does news look okay?
2) Apply patch
3) Refresh staff client.
    - Does news look the same?

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Safe no op action

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>