ControllerRootViewContainer could be typed.

The implementation could be like this:
```
public final class TypedControllerRootViewContainer<CONTROLLER>: ControllerRootViewContainer

public class ControllerRootViewContainer: UIView, Configurable
```

It would allow switching in styles in Configuration like this:
```
controllerRoot = { view in
    if view is TypedControllerRootViewContainer<LoginController> { ... }
}
```