Expose navBarTransparent to Js

closes #21

android/app/src/main/java/com/reactnativenavigation/params/parsers/StyleParamsParser.java

         result.selectedTopTabIndicatorHeight = getInt("selectedTopTabIndicatorHeight", getDefaultSelectedTopTabIndicatorHeight());
         result.selectedTopTabIndicatorColor = getColor("selectedTopTabIndicatorColor", getDefaultSelectedTopTabIndicatorColor());
 
-        // TODO: Uncomment once we support drawBelowTopBar again
-        //result.drawScreenBelowTopBar = params.getBoolean("drawBelowTopBar", isDefaultScreenBelowTopBar());
-        result.drawScreenBelowTopBar = !result.topBarTransparent;
+        result.drawScreenBelowTopBar = params.getBoolean("drawBelowTopBar", getDefaultScreenBelowTopBar());
+        if (result.topBarTransparent) {
+            result.drawScreenBelowTopBar = false;
+        }
 
         result.bottomTabsHidden = getBoolean("bottomTabsHidden", getDefaultBottomTabsHidden());
         result.drawScreenAboveBottomTabs = !result.bottomTabsHidden &&
         return AppStyle.appStyle != null && AppStyle.appStyle.bottomTabsHidden;
     }
 
-    private boolean isDefaultScreenBelowTopBar() {
-        return AppStyle.appStyle == null || AppStyle.appStyle.drawScreenBelowTopBar;
+    private boolean getDefaultScreenBelowTopBar() {
+        return AppStyle.appStyle != null && AppStyle.appStyle.drawScreenBelowTopBar;
     }
 
     private boolean getDefaultTopTabsHidden() {

android/app/src/main/java/com/reactnativenavigation/screens/SingleScreen.java

     @Override
     protected void createContent() {
         contentView = new ContentView(getContext(), screenParams.screenId, screenParams.navigationParams);
-        addView(contentView, createLayoutParams());
+        addView(contentView, 0, createLayoutParams());
     }
 
     protected LayoutParams createLayoutParams() {

src/deprecated/platformSpecificDeprecated.android.js

   let ret = {
     statusBarColor: originalStyleObject.statusBarColor,
     topBarColor: originalStyleObject.navBarBackgroundColor,
+    topBarTransparent: originalStyleObject.navBarTransparent,
     collapsingToolBarImage: originalStyleObject.collapsingToolBarImage,
     collapsingToolBarCollapsedColor: originalStyleObject.collapsingToolBarCollapsedColor,
     titleBarHidden: originalStyleObject.navBarHidden,