feat(screen-orientation): Added Screen Orientation Plugin #342 (#366)

* Added OneSignal wrapper

* documentation

* Changes for callback of notification revieced

* fixes for @Cordova decorators without Promise return

* Merge

* Improvements to OneSignal
extended init function with notificationOpenedCallback as an optional parameter

* Platforms removed
OneSignal supports more than only these 3 platforms. It's available to nearly all Cordova platforms.

* Init method turned into observable

* Screen Orientation Plugin added. Closes #342

src/index.ts

@@ -60,6 +60,7 @@ import {NativeStorage} from './plugins/nativestorage';
 import {MediaPlugin} from './plugins/media';
 import {Network} from './plugins/network';
 import {OneSignal} from './plugins/onesignal';
+import {ScreenOrientation} from './plugins/screen-orientation';
 import {PinDialog} from './plugins/pin-dialog';
 import {Printer} from './plugins/printer';
 import {Push} from './plugins/push';
@@ -145,6 +146,7 @@ export {
   NativeStorage,
   Network,
   OneSignal,
+  ScreenOrientation,
   PinDialog,
   Screenshot,
   SecureStorage,
@@ -219,6 +221,7 @@ window['IonicNative'] = {
   Printer: Printer,
   Push: Push,
   OneSignal: OneSignal,
+  ScreenOrientation: ScreenOrientation,
   PinDialog: PinDialog,
   SafariViewController: SafariViewController,
   Screenshot: Screenshot,