重写了节点的view、viewmodel关系，实现了对画布元素的选取功能，重构了底层依赖，添加了对net .Framework4.6.1以上的Framework类库支持

NodeFlow/Model/SingleFlipflopNode.cs

@@ -1,11 +1,12 @@
-using Serein.NodeFlow;
+using Serein.Library.Api;
+using Serein.Library.Core.NodeFlow;
 
 namespace Serein.NodeFlow.Model
 {
 
     public class SingleFlipflopNode : NodeBase
     {
-        public override object Execute(DynamicContext context)
+        public override object Execute(IDynamicContext context)
         {
             throw new NotImplementedException("无法以非await/async的形式调用触发器");
         }