updated polish translation

Hi!

I've made some mistakes in my polish translation included in 2.0.0 versions and up.
Especially one thing (which i didn't notice) looks wierd - two english words were
translated as the same polish word (this word has two meanings, so it was
theoretically correct - but looks strang in the menu.

Also, my gmail.com email address no longer exists,
mostly because of a bit 'political' reasons;)

The translation file is included.