This demo puts to practice the concepts explained in this article by objc.io: http://www.objc.io/issues/9-strings/string-localization/#plural-and-gender-support
By running the app in English or Polish we can see the demonstration of the different types of plurals.
The polish plural rules were adopted from this website: http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html