If you had to suss out the next big foodie trend, you probably wouldn't visit a hospital cafeteria for gourmet inspiration. But that's exactly the origin of uber-trendy overnight oats, an idea born of a Swiss doctor back in 1900 who was looking for an easy way to serve up the numerous benefits of oatmeal to his hospital patients. The original meal, muesli, roughly translates to "mash-up" and that's what overnight oats are: a mix of raw oats, soaked overnight in water, milk, or yogurt, and then served, uncooked, with fruits…