v0.1.6

Updated: the Polish (pol-PL) buttons and menu items use the infinitive ("Edytować", "Usunąć", "Zapisać i zakończyć"), as the Exponential administration does since its Polish catalogue was corrected (pol-PL GUIDE.md: buttons, menu items and action tooltips in the infinitive). Messages, headings and longer instructions are unchanged. Translation file only; no code change.