Always add screens behind TopBar

This resolves a few edge cases where screens overlapped the TopBar

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/stack/StackController.java

         view.setLayoutParams(new RelativeLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT));
         child.setWaitForRender(resolvedOptions.animations.push.waitForRender);
         presenter.applyLayoutParamsOptions(resolvedOptions, view);
-        getView().addView(view);
+        getView().addView(view, getView().getChildCount() - 1);
     }
 
     public void setRoot(ViewController child, CommandListener listener) {
         child.setLayoutParams(new RelativeLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT));
         Options options = resolveCurrentOptions();
         presenter.applyLayoutParamsOptions(options, child);
-        stackLayout.addView(child);
+        stackLayout.addView(child, 0);
     }
 
     private void onNavigationButtonPressed(String buttonId) {

lib/android/app/src/test/java/com/reactnativenavigation/viewcontrollers/stack/StackControllerTest.java

         StackController uut = createStack(Arrays.asList(child1, child2, child3, child4));
         assertThat(uut.getChildControllers().size()).isEqualTo(4);
         assertThat(uut.getView().getChildCount()).isEqualTo(2);
-        assertThat(uut.getView().getChildAt(1)).isEqualTo(child4.getView());
+        assertThat(uut.getView().getChildAt(0)).isEqualTo(child4.getView());
     }
 
     @Test
         parent.ensureViewIsCreated();
         parent.push(uut, new CommandListenerAdapter());
         uut.onViewAppeared();
-        assertThat(parent.getView().getChildAt(1)).isEqualTo(uut.getView());
+        assertThat(parent.getView().getChildAt(0)).isEqualTo(uut.getView());
     }
 
     @Test