Fix to the list problem

I've fixed the list problem for how you have it set up. As it stands, the Index view should show a list of the Gamme objects added in the current session (though I think you're using Html.DisplayFor wrong).
I've also cleaned up a lot of whitespace in the code to make it more readable.

I'm not a big fan of using session variables though, I've added more to my stackoverflow answer. http://stackoverflow.com/a/16709195/1278481