Unbind references from container on scene unload

Zenject doesn't properly clear reference from scene container when scene
is unloaded. This results in memory leak when loading and unloading
scenes.

Fixed the issue by unbinding all reference from scene container when
SceneContext component is destroyed.

modesttree#246

UnityProject/Assets/Plugins/Zenject/Source/Runtime/Install/Contexts/SceneContext.cs

@@ -136,6 +136,11 @@ protected override void Awake()
             }
         }
 
+        protected virtual void OnDestroy()
+        {
+            _container.UnbindAll();
+        }
+
 #if UNITY_EDITOR
         protected override void ResetInstanceFields()
         {