重构了底层，方便向Android、Web、Linux进行跨平台迁移

NodeFlow/ConnectionType.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Serein.NodeFlow
+{
+    public enum ConnectionType
+    {
+        /// <summary>
+        /// 真分支
+        /// </summary>
+        IsSucceed,
+        /// <summary>
+        /// 假分支
+        /// </summary>
+        IsFail,
+        /// <summary>
+        /// 异常发生分支
+        /// </summary>
+        IsError,
+        /// <summary>
+        /// 上游分支（执行当前节点前会执行一次上游分支）
+        /// </summary>
+        Upstream,
+    }
+
+
+}