Merge pull request #738 from sdlu1992/task/task_v1.12.13_support_hotfixes

opt: 添加删除生命周期的方法

lib/flutter_boost.dart

@@ -193,7 +193,20 @@ class FlutterBoost {
           BoostContainerLifeCycleObserver observer) =>
       _observersHolder.addObserver<BoostContainerLifeCycleObserver>(observer);
 
+  ///unregister for Container changed callbacks
+  void removeContainerObserver(BoostContainerObserver observer) =>
+      _observersHolder.removeObserver<BoostContainerObserver>(observer);
+
+  ///unregister for Container lifecycle callbacks
+  void removeBoostContainerLifeCycleObserver(
+      BoostContainerLifeCycleObserver observer) =>
+      _observersHolder.removeObserver<BoostContainerLifeCycleObserver>(observer);
+
   ///register callbacks for Navigators push & pop
   void addBoostNavigatorObserver(NavigatorObserver observer) =>
       ContainerNavigatorObserver.boostObservers.add(observer);
+
+  ///unregister callbacks for Navigators push & pop
+  void removeBoostNavigatorObserver(NavigatorObserver observer) =>
+      ContainerNavigatorObserver.boostObservers.remove(observer);
 }