[i18n] Updated polish translation for 3.0.5

[Krzysztof Kozlowski]

Hi

It seems that polish translation is very outdated... Current pl_PL.po
hasn't been touched for 4 years. I wish to send my updated
translation, but it still is only a part of all locale texts. In the
near future I will translate rest of text.

http://acn.waw.pl/koziol/projekty/horde/locale/horde.mo
http://acn.waw.pl/koziol/projekty/horde/locale/pl_PL.po.diff
http://acn.waw.pl/koziol/projekty/horde/locale/pl_PL.po

Krzysztof Kozłowski