Added code and a setting to allow unfold of child menus on hover

[Marcool04]

Hi there! First of all, thank you for this nice little menu, it's been really handy. There was a feature I was asked for that was to unfold sub-menus on hover over the parent. The request was justified by the fact that you wouldn't have to understand that the little arrow means "click to unfold" (which I agree, is fairly clear, but that's apparently not the case for everybody), and also avoids confusion when you click on a parent element's link and go to that page, when the sub-menu possibly goes unnoticed. So here is my proposed way to do that. I'm absolutely no expert in jQuery, so if anything is not clean or standard, I'm very pleased to hear criticism. Best regards, Mark.