Rainlendar 2.8

- The to do list now takes the start/due time into account also when sorting the list.
- Window variables with predefined list didn't work when localized texts were used. Fixed.
- Week number in the week view wasn't adjusted by the "Week number delta" setting. Fixed.
- Copy group adds postfix ".x.y" to the "id" for the copied items.
- Old languages are removed from the config folder on startup if there is a newer one in the program folder.
- CSV export wrote the first instance of a recurring event twice to the file. Fixed.
- The operating system's default language is used automatically instead English on new installations.