i18n: Added datepicker localization for Swiss Italian and Swiss Romansh

Previous Pull Request:
https://github.com/jquery/jquery-ui/pull/643#issuecomment-11729328

So far the date format for Swiss Italian and Romansh aren't correct. We're using dd.mm.yy instead of dd/mm/yy. 'de-CH' isn't necessary cause the German localization has the same date format as we use in Switzerland and 'fr-CH' is already written.