event add/propose : on writing title show with ajax similar titles the same day and category

[agilare]

Events are often added double, because it can be added by multiples different organizers, who don't have coordinated their promotion.
In order to avoid doubles, we can add a small tool showing to user filling the event add form, (very) similar events if it exists.
It could be implemented as a dynamic info box with ajax searching similar events based on date, category, place and title (like suggestions in Stackoverflow questions or GitHub issues). For example when an user is adding an event, if an other event the same day, in same category and place and with similar words in the title, an info box would display the similar event and suggest to contact the organizer who added the first event if the user wants to do modifications; as a last resort he can contact webmasters of La décadanse for that.