IEnumerable<T>.OrderBySelf()

It can be common to simply order a result by itself. e.g.

```csharp
int[] a = new[] {1, 5, 9, 2, 4, 3, 7, 8, 0};
var ordered = a.OrderBy(b => b);
```

Could collapse this into an `OrderBySelf()` with a variants that order descending, and variants that take an `IComparer`. Also the `ThenBy`/`ThenByDescending` variants too.

