#38 Updated Polish Translation for v. 1.6.1

[Maciej]

Hi, here is updated translation file. Some strings are changed. Please compile it.
In source file not string "Acquired pages".
Polish translation for missing string:
Acquired pages - Zeskanowane strony

[Matteo Rossi]

Thank you very much for the updated translation! I uploaded the new compiled version. Notice that it might take some time for it to be updated on the various Sourceforge mirrors. Please tell me if everything works correctly