从节点Model解耦出容器接口，重新设计了节点的保存、加载。

NodeFlow/Model/SingleScriptNode.cs

@@ -28,6 +28,13 @@ namespace Serein.NodeFlow.Model
     /// </summary>
     public partial class SingleScriptNode : NodeModelBase
     {
+
+        /// <summary>
+        /// 脚本节点是基础节点
+        /// </summary>
+        public override bool IsBase => true;
+
+
         private IScriptFlowApi ScriptFlowApi { get; }
 
         private ASTNode mainNode;