Opportunity

Intoducing Opportunity, a Meetup planifier (or planner, if we listen to @xymus, will correct that along with your remarks).

So, here's the long awaited Opportunity that will be the cornerstone of every ~~nutritious breakfast~~ Latece weekly seminar.

Maybe more once finished, let's conquer the world with Nit's amazing abilities for easy web development.

Also, a function was missing from SQLite, I needed it so, here it is as well.
Si les `on delete cascade` ne fonctionne pas, tu es peut-être mieux de le noter, il ne faudrait pas s'y fier.