Move MatterControl source code into a subdirectory

original/MatterControlLib/Utilities/SelectedListItems.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+
+namespace MatterHackers.MatterControl
+{
+	public class SelectedListItems<T> : List<T>
+	{
+		public event EventHandler OnAdd;
+
+		public event EventHandler OnRemove;
+
+		new public void Add(T item)
+		{
+			base.Add(item);
+			if (null != OnAdd)
+			{
+				OnAdd(this, null);
+			}
+		}
+
+		new public void Remove(T item)
+		{
+			base.Remove(item);
+			if (null != OnRemove)
+			{
+				OnRemove(this, null);
+			}
+		}
+
+		// Also fire OnRemove on Clear
+		new public void Clear()
+		{
+			base.Clear();
+			if (null != OnRemove)
+			{
+				OnRemove(this, null);
+			}
+		}
+	}
+}