feat: move NgZone to Stream/Observable-based callback API

BREAKING CHANGES:
- deprecates these methods in NgZone: overrideOnTurnStart, overrideOnTurnDone, overrideOnEventDone, overrideOnErrorHandler
- introduces new API in NgZone that may shadow other API used by existing applications.

modules/angular2/test/public_api_spec.ts

@@ -467,6 +467,7 @@ var NG_API = [
   'ElementRef.parentView',
   'ElementRef.parentView=',
   'ElementRef.renderView',
+  'ErrorHandlingFn:dart',
   'Output',
   'Output.bindingPropertyName',
   'EventEmitter',
@@ -795,12 +796,22 @@ var NG_API = [
   'NgSwitchWhen',
   'NgSwitchWhen.ngSwitchWhen=',
   'NgZone',
+  'NgZone.hasPendingAsyncTasks',
+  'NgZone.hasPendingMicrotasks',
+  'NgZone.hasPendingTimers',
+  'NgZone.onError',
+  'NgZone.onEventDone',
+  'NgZone.onTurnDone',
+  'NgZone.onTurnStart',
   'NgZone.overrideOnErrorHandler()',
   'NgZone.overrideOnEventDone()',
   'NgZone.overrideOnTurnDone()',
   'NgZone.overrideOnTurnStart()',
   'NgZone.run()',
   'NgZone.runOutsideAngular()',
+  'NgZoneError',
+  'NgZoneError.error',
+  'NgZoneError.stackTrace',
   'NoAnnotationError',
   'NoAnnotationError.message',
   'NoAnnotationError.stackTrace',
@@ -1107,6 +1118,7 @@ var NG_API = [
   'WrappedValue.wrapped',
   'WrappedValue.wrapped=',
   'WtfScopeFn:dart',
+  'ZeroArgFunction:dart',
   'applicationCommonBindings()',
   'asNativeElements()',
   'bind()',