Addquotes: ignoring recommandations shouldn't be irrevocable

As of today, if the `addquotes` feature suggests to define "games" to be a synonym of "game" and the user refuses, then `addquotes` will never propose again to her to define "games" to be a synonym of "game". Maybe it could make sense to have an option that says "I don't want to do this for this occurrence of 'games', but should you stumble upon 'games' again, then ask me again".