Add support for Android TV devices

Summary:
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* To be on par with Apple TV support, this makes it possible to run React Native apps on Android TV devices (See also: https://react-native.canny.io/feature-requests/p/android-tv-support)
* These changes also make it possible to navigate through the app using D-PAD buttons that are present on some mobile devices
* Since these changes affect, among others, `ReactRootView.java` and `Touchable.js` code and are closely related to Apple TV implementation, it makes sense for them to be included in the core

 - React native apps can be launched on Android TV devices and properly render their content
 - Navigation is possible using left, right, top, bottom arrows from the remote (or D-PAD)
 - Touchable components can handle D-PAD center button press events and correctly fire their `onPress` handlers
 - Touchable components will receive `onPressIn` and `onPressOut` events and can react to focus/blur changes appropriately (just like on Apple TV)
 - `Platform` constants allow to check if the react-native app is running on TV (`Platform.isTV`)
 - `ScrollView`s behave correctly (same as native implementation) when switching to view outside bounds – that is, the container would scroll such that the newly focused element is fully visible
 - Native "clicking" sounds are played when moving between focusable elements
 - Play/Pause click event is send to `TVEventHandler`
 - Rewind and FastForward events are send to `TVEventHandler`
 - Back button behaves as a normal Android back button
 - Diagonal buttons work correctly on Android TV, e.g. if there is no button directly to the right from the focused one, but there is one to the right but a bit higher/lower it will grab focus
 - Dev menu can be accessed by long pressing fast forward button

A demo showing RNTester app running on Android TV device (Amazon Fire TV Stick) can be found here:
[![RNAndroidTVDemo](http://img.youtube.com/vi/EzIQErHhY20/0.jpg)](http://www.youtube.com/watch?v=EzIQErHhY20)

- `TextInput` will not work on Android TV devices. There's an issue with native `ReactEditText` implementation that prevents it from receiving focus. This makes it impossible to navigate to `TextInput`.
This will be fixed next, but will be included in a separate Pull Request
- ~Overlay permissions cannot be granted on Android TV devices running Android version >= 6.0
This is because the overlay permission can only be granted by firing an Intent to open settings page (`ACTION_MANAGE_OVERLAY_PERMISSION`). Since this page does not exist on TV devices the permission cannot be requested. This will make the app crash when trying to open dev menu (⌘+M) or displaying a redbox error.
Note: This does not affect devices running Android version < 6.0 (for example Amazon Fire TV Stick)~
This is now fixed by: facebook/react-native#16596

* Launch the RNTester app on Android TV device.
  * Ensure it launches without a crash
  * Ensure basic navigation is possible
  * Ensure Touchable components can receive select events
* Ensure the changes do not break current Android and iOS mobile devices functionality.
* Ensure the changes do not break current Apple TV functionality.

[RNAndroidTVDemo video](http://img.youtube.com/vi/EzIQErHhY20/0.jpg)

* Added `ReactAndroidTVViewManager` that handles TV `KeyEvent`s and dispatches events to JS - This is the core that enables basic navigation functionality on Android TV devices
* Following the above change we copy `TVEventHandler.ios.js` into `TVEventHandler.android.js` to enable JS to pick up those native navigation events and dispatch them further to subscribed views. (Note: We do not have a native `TVNavigationEventEmitter` implementation on Android, thus this file is slightly modified, e.g. it does pass `null` to `NativeEventEmitter` constructor)
* Added `uiMode` to `AndroidInfoModule`. (**Note**: This required changing `extends BaseJavaModule` to `extends ReactContextBaseJavaModule` to be able to use `getSystemService` which requires `Context` instance!
* Added `isTV` constants to both `Platform.ios.js` (keeping the deprecated `isTVOS` as well) and `Platform.android.js`
* Changed condition check on `Touchable.js` to use the newly added `isTV` flag to properly handle TV navigation events on Android as well
* Added `LEANBACK_LAUNCHER` to `RNTester` `intent-filter` so that it is possible to launch it on Android TV devices.
* See also a PR to `react-native-website` repo with updated docs for Android TV: facebook/react-native-website#59

 - [ ] Fix `TextInput` components handling by allowing them to be focused and making a proper navigation between them (and/or other components) possible. One thing to note here that the default behavior to immediately open software keyboard when focused on `TextInput` field will need to be adjusted on Android TV as well)
 - [x] Fix overlay permissions issue by changing the way redbox/dev menu are displayed (see: facebook/react-native#16596)
 - [ ] Adjust placement of TV-related files (e.g. the `TVEventHandler.js` file is placed inside `AppleTV` directory which is not accurate, since it does handle Android TV events as well)

Previous discussion: software-mansion-labs/react-native#1
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  CATEGORY
[----------]        TYPE
[ CLI      ]   [-------------]      LOCATION
[ DOCS     ]   [ BREAKING    ]   [-------------]
[ GENERAl  ]   [ BUGFIX      ]   [-{Component}-]
[ INTERNAL ]   [ ENHANCEMENT ]   [ {File}      ]
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[CATEGORY] [TYPE] [LOCATION] - MESSAGE

 EXAMPLES:

 [IOS] [BREAKING] [FlatList] - Change a thing that breaks other things
 [ANDROID] [BUGFIX] [TextInput] - Did a thing to TextInput
 [CLI] [FEATURE] [local-cli/info/info.js] - CLI easier to do things with
 [DOCS] [BUGFIX] [GettingStarted.md] - Accidentally a thing/word
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 [INTERNAL] [FEATURE] [./scripts] - Added thing to script that nobody will see
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[ANDROID] [FEATURE] [TV] - Added support for Android TV devices
Closes facebook/react-native#16500

Differential Revision: D6536847

Pulled By: hramos

fbshipit-source-id: 17bbb11e8583b97f195ced5fd9762f8902fb8a3d

android/app/src/main/AndroidManifest.xml

@@ -20,9 +20,14 @@
     android:minSdkVersion="16"
     android:targetSdkVersion="23" />
 
+  <!--
+  android:icon is used to display launcher icon on mobile devices.
+  android:banner is used to display a rectangular banned launcher icon on Android TV devices.
+  -->
   <application
       android:name=".RNTesterApplication"
       android:allowBackup="true"
+      android:banner="@drawable/tv_banner"
       android:icon="@drawable/launcher_icon"
       android:label="@string/app_name"
       android:theme="@style/Theme.ReactNative.AppCompat.Light" >
@@ -34,6 +39,8 @@
       <intent-filter>
         <action android:name="android.intent.action.MAIN" />
         <category android:name="android.intent.category.LAUNCHER" />
+        <!-- Needed to properly create a launch intent when running on Android TV -->
+        <category android:name="android.intent.category.LEANBACK_LAUNCHER" />
       </intent-filter>
       <intent-filter>
         <action android:name="android.intent.action.VIEW" />