Bug 16554: rewrite mandatory and sample data - pl-PL

Bug 16554: rewrite mandatory and sample data - pl-PL

More changes to pl-PL files

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 28191a538b8f3bed698f1e67acca156c5b64ebea)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
(cherry picked from commit 9d11edefeabbe509e45d8fac7064f5e106533c50)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>