Corrected Russian and added Ukrainian l10n + other changes

Hi Jörn,    
Here's what I've done:    
- Updated Russian localization according to my comment on its commit;
- Added Ukrainian localization;
- Updated French and Swedish localizations as they didn't contain messages for week, month, year and years;
- Added support for the day before yesterday since this day is called in one word in many languages (cf. vorgestern in German). Updated localizations adding this message.