Added debug display for selection

PixiEditor/Models/DataHolders/Selection.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Diagnostics;
 using System.Linq;
 using System.Windows.Media;
 using PixiEditor.Helpers;
@@ -9,6 +10,7 @@ using PixiEditor.Models.Position;
 
 namespace PixiEditor.Models.DataHolders
 {
+    [DebuggerDisplay("{SelectedPoints.Count} selected Pixels")]
     public class Selection : NotifyableObject
     {
         private readonly Color selectionBlue;