Allow to change translations by uploading a new locale file

As a web-hosting provider, I would like to be able to modify existing translations by uploading a new translations file so that you don't have to delete locale before uploading the corrected one.

Currently if you upload a new translation file, only the non translated strings are updated. To update a translation you have to delete the locale and then upload the new one. This works but also means that cPanel users who visit cPanel during the update are shown cPanel in a different language than the one they have chosen.