Polish .po file merged from Transifex

Cleared up the mess around Polish translation by manually downloading .po file from Transifex - which contained the latest set of messages via 560bcab1fcc3ce08bb7f06b2c197c15f5af46bc9, and which I translated to Polish in Transifex earlier - and merging it with the recent translation improvements - which I've pull-requested earlier today via 8c530ac3ad85634d37b404b8e82069223f97af76.

**tl;dr** The .po file for Polish locale should be all up-to-date now.

_Note to self: always check for the newer version of .po file before tinkering with Rosetta locally. Will now eat some Burger King as a penance._