UI/feature updates

• Internationalize the entire app:
  • A new "user preferences" dialog allows configuring the language. By default, the language is auto-detected from the browser language.
  • Units can also be switched to the US Customary system in the user preferences.
  • The German translation is finished an Norwegian and Russian translations have been started. Translations are created collectively on Weblate.
• Add shower POI type, simplify POI categories and add “All amenities”, “All touristic places”, “All sports facilities” and “All shops” POI types (#261).

Technical changes

• The FacilMap modules are now internationalized using i18next. Find details about how to adjust the language configuration in the documentation.