Polish translation update for version 5

[wnagrodzki]

First commit is purely technical with updates applied from darktable.pot to pl.po. I advise focusing on the subsequent commits during review. There are still some inconsistencies and mistranslations but fixing those is out of scope of this pull request. The aim of this pull request was to update outdated translations and provide missing ones.

[victoryforce]

I advise focusing on the subsequent commits during review.

Translations do not go through reviews.

[TurboGit]

Translations do not go through reviews.

We could if we had lot of devs and all languages covered by more than one dev :) But that a luxury we can't afford :)

[Jankowski-J]

In the latest (5.0.0) windows installation, there's no Polish language available in settings.
What are the requirements for this language to be available in application?

[wnagrodzki]

It will be included in the next release 5.0.1

[victoryforce]

What are the requirements for this language to be available in application?

@Jankowski-J These are requirements not only for Polish, but for all translations:
No more than 20 untranslated strings and no more than 50 fuzzy (outdated due to changes in the original) translations at the time of including translations in the release. That is, a total of 70 untranslated GUI elements.