* added tab selected event

* changed event name to `bottomTabSelected`

* Fix navigator buttons immutability issue

* Show fab in pushed screen

* added status bar color scheme for single screen which isn't pass on push. Set "statusBarTextColorSchemeSingleScreen" on the navigatorStyle

* make statusBarTextColorSchemeSingleScreen preferred option when both statusBarTextColorScheme and statusBarTextColorSchemeSingleScreen are exists

* Pass showAsAction property to native. It was left out by mistake
* Support textual icons in contextual menu

The event is sent to the top most screen displayed in the current screenStack.

call setButtons with empty fab object to remove it

* Added default testId to registered components

* Added default testID to registered components

* Corrected screenId to screenID

* Added default testId to registered components

* Added default testID to registered components

* Less intrusive collapsing implementation

In order for a screen to implement collapsingTopBar, it had to define
a specific set of style properties such as drawUnderTabBar or
drawUnderNavBar. This commit aims to make implementing collapsingTopBar
less intrusive by inferring these properties from hideTitleBarOnScroll.

This commit introduces a few fixes and changes related to
the collapsingTopBar mechanism.

1. Screens are now drawn under bottomTabs if titleBarHideOnScroll
   is true.

2. TitleBarHideOnScroll can be passed in AppStyle.

3. ScrollView is detected properly after it gets detached due to large
   diff in render.

4. Take BottomTabs height into account when measuring collapsing
   screens.

Now the style parameter is used inside RCCDrawerController but it's not passed through startTabBasedApp/startSingleScreenApp. Passing the style parameter allows to disable sidebar shadow trough style.drawerShadow.

related to #557 #474 #125

https://github.com/wix/react-native-navigation/issues/297