Translation - English-Spanish - Duplicated-indexes-upload

Upload items are a sound or an illustration. They are integrated in the wiki article and can be recorded/edited by the visitor. Each upload item is identified by a number (called the "index"). When editing a wiki article, if one of the indexes appears twice, it will be replaced by the same soudn or illustration. Usually it's not what we want to do, that's way we must display a warning.