* Add initialTabIndex support to RCCTabBarController

* Add initialTabIndex support to BottomTabsLayout

closes #1694

fixes #1675

To match the rest of the styling

As the screen api document mentions that it can be done statically, it's best to mention it here as well.

* Revert "Add custom bar button item class (#1641)"

This reverts commit 80ae102456.

* Revert "Export `Navigator` class for public use (#1647)"

This reverts commit 1770113321.

* Revert "Hide back button when calling resetTo (#1469)"

This reverts commit 518e372e05.

* Revert "Add isRootLaunched implementation on Android"

This reverts commit 6f4aca32a6.

* Revert "Fixed LightBox not updating overlay width/height on rotate (#1461)"

This reverts commit 54d2531720.

This allows for custom React Native views to be rendered as a bar button item in the navigation bar.

* Make Navigator Public

* Make Screen.js export both Screen and Navigator

* Update Navigation.js to import Screen correctly

* Make Navigator public for Android too

* Forgot to export after importing

* ESLint fix

* ESLint fix

* ESLint Fix

* ESLint Fix

returns true if NavigationActivity is resumed (startApp was called)

* Fixed LightBox not updating overlay width/height on rotate

* Cleaned up bounds

* Removed unneeded call

See https://github.com/wix/react-native-navigation/issues/1446#issuecomment-319858633

Fixes #1609

* update docs for ios drawer animations in top-level-api section

* update docs for ios drawer animations in top-level-api section

https://github.com/wix/react-native-navigation/issues/1446

To prevent race condition happening when the event was sent before the screen was mounted

* Update top-level-api.md (Added forgotten styles)

Added forgotten drawer style props.

* Added iOS only words to style objects

fixes #1586 #1585 #1584

* added method for getting the currently visible screen ID. Can be useful to decide if logic should be applied according to screen visibility, for example: set buttons/title dynamically, or even determine that you don’t need to show the same screen again if it’s the current one that’s showing

* Implement getCurrentlyVisibleScreenId on Android

Can be used statically:
Navigation.getCurrentlyVisibleScreenId() - returns the unique screen
instance id

With a navigator instance:
await this.props.navigator.screenIsCurrentlyVisible() - resolves a
promise that checks if the current screen is visible

* Remove extra line-break to fix rendering list in doc site.

* Add In-App Notification

* Add screen visibility listener which can be registered globally

API
new ScreenVisibilityListener({
    willAppear: ({screen, timestamp}) => console.log(`Displaying screen ${screen}`),
    didAppear: ({screen, timestamp}) => console.log(`Screen ${screen} displayed in ${Date.now() - timestamp} millis`)
  }).register();

todo
* Add timestamp to modal, resetTo
* implement unregister
* implement iOS

* Add global screen visibility listener to example app

* Think I better assign a value to emitter

* Send timestamp in resetTo

* Moved listener to library, it can be deleted from the app

* Add push and resetTo buttons to pushed screens

* Send appear/disappear events after animation ends

* Pass pop timestamp from js

* Send timestamp in popToRoot

* Add popToRoot button in push screen

* Add few navigation buttons to modal screen

* Pass timestamp to tabs

relevant only to first/initial tab

* Update timestamp when navigating between BottomTabs

* Send screen visible events after modal dismiss

* log willDisappear and didDisappear

* Report both start and end timestamps

* Implement unregister

* Send NavigationType parameter in visibilityEvent

This indicates the type of the navigation command that triggered the visibility change

* Rename pushInitialScreen to more explicit name

* Fix duplicate initialScreen visibility events

* Update screen visibility log statement

* Show popToRoot in modal screen only if screens were pushed

* implement global screen event for iOS

* fix lint issues