Changed Slot in RelayNode to ProxySlot;

Changed PullData and PushData from SlotExtension to ISlot;

Added BackTraceExecutableNode;

Removed IExecutable from RelayNode;

Runtime/Models/Nodes/NodeGroupData.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+
+namespace Misaki.GraphView
+{
+    [Serializable]
+    public struct NodeGroupData
+    {
+        public string id;
+        public string name;
+        public List<string> nodeIds;
+
+        public NodeGroupData(string groupName)
+        {
+            id = Guid.NewGuid().ToString();
+            name = groupName;
+            nodeIds = new List<string>();
+        }
+    }
+}