title: Flutter navigation for part of screen
body: <p>How can I push a widget in the frame of another widget? For example I have a Column with 2 Containers where every Container takes half of the screen. I'd like to make a navigation e.g. only in the bottom container. The same logic as in iOS when the container view has it's own UINavigationController.</p>
  
  <p>As I understood MaterialPageRoute can push widgets only to fullscreen and there aren't any other Route classes, except abstract ones. Maybe I should make my own subclass of ModalRoute/TransitionRoute?</p>