Porting showplan code from ssms (#1280)

* Porting showplan code from ssms

* Moving showplans bits to a subfolder

* code cleanup

* Remvoing unnecssary conditional visibility

src/Microsoft.SqlTools.ServiceLayer/ShowPlan/ShowPlanGraph/Comparison/SkeletonNode.cs

@@ -0,0 +1,88 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+
+namespace Microsoft.SqlTools.ServiceLayer.ShowPlan.ShowPlanGraph.Comparison
+{
+    public class SkeletonNode
+    {
+        public Node BaseNode {get; set;}
+        public List<SkeletonNode> MatchingNodes { get; set; }
+        public bool HasMatch { get { return MatchingNodes.Count > 0; } }
+        public SkeletonNode ParentNode { get; set; }
+        public IList<SkeletonNode> Children { get; set; }
+
+        public int GroupIndex 
+        { 
+            get
+            {
+                return this.BaseNode.GroupIndex;
+            }
+            set
+            {
+                this.BaseNode.GroupIndex = value;
+            }
+        }
+
+        public SkeletonNode(Node baseNode)
+        {
+            baseNode[NodeBuilderConstants.SkeletonNode] = this;
+            this.BaseNode = baseNode;
+            this.Children = new List<SkeletonNode>();
+            this.MatchingNodes = new List<SkeletonNode>();
+        }
+
+        /// <summary>
+        /// Adds node to children collection and sets this node as parent of the child
+        /// </summary>
+        /// <param name="child"></param>
+        public void AddChild(SkeletonNode child)
+        {
+            child.ParentNode = this;
+            this.Children.Add(child);
+        }
+
+        public void ChangeSkeletonGroupIndex(int groupIndex)
+        {
+            this.GroupIndex = groupIndex;
+            foreach (SkeletonNode child in this.Children)
+            {
+                child.ChangeSkeletonGroupIndex(groupIndex);
+            }
+        }
+
+        public void AddMatchingSkeletonNode(SkeletonNode match, bool ignoreDatabaseName, bool matchAllChildren=true)
+        {
+            this.BaseNode[NodeBuilderConstants.SkeletonHasMatch] = true;
+            if (matchAllChildren == true)
+            {
+                SkeletonManager manager = new SkeletonManager();
+                foreach (SkeletonNode baseChild in this.Children)
+                {
+                    foreach (SkeletonNode matchChild in match.Children)
+                    {
+                        // make sure this is the right child to match
+                        if (baseChild.BaseNode.IsLogicallyEquivalentTo(matchChild.BaseNode, ignoreDatabaseName))
+                        {
+                            baseChild.AddMatchingSkeletonNode(matchChild, ignoreDatabaseName, matchAllChildren);
+                        }
+                    }
+                }
+            }
+            this.MatchingNodes.Add(match);
+        }
+
+        public Graph GetGraph()
+        {
+            return this.BaseNode.Graph;
+        }
+
+    }
+}