Made the re/undo code from the branch work in this, this is a manual copy as something went horribly wrong with the repository. Before building I first want to check if everything is there.[skip ci]

Greenshot/Memento/AddElementsMemento.cs

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+/*
+ * Greenshot - a free and open source screenshot tool
+ * Copyright (C) 2007-2015 Thomas Braun, Jens Klingen, Robin Krom
+ * 
+ * For more information see: http://getgreenshot.org/
+ * The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 1 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+using Greenshot.Drawing;
+using Greenshot.Plugin.Drawing;
+
+namespace Greenshot.Memento
+{
+	/// <summary>
+	/// The AddElementMemento makes it possible to undo adding an element
+	/// </summary>
+	public class AddElementsMemento : IMemento
+	{
+		private IDrawableContainerList _containerList;
+		private Surface _surface;
+
+		public AddElementsMemento(Surface surface, IDrawableContainerList containerList)
+		{
+			_surface = surface;
+			_containerList = containerList;
+		}
+
+		public void Dispose()
+		{
+			Dispose(true);
+		}
+
+		protected virtual void Dispose(bool disposing)
+		{
+			if (disposing)
+			{
+				if (_containerList != null)
+				{
+					_containerList.Dispose();
+				}
+			}
+			_containerList = null;
+			_surface = null;
+		}
+
+		public bool Merge(IMemento otherMemento)
+		{
+			return false;
+		}
+
+		public IMemento Restore()
+		{
+			// Store the selected state, as it's overwritten by the RemoveElement
+			bool selected = _containerList.Selected;
+
+			var oldState = new DeleteElementsMemento(_surface, _containerList);
+
+			_surface.RemoveElements(_containerList, false);
+
+			// After, so everything is gone
+			_surface.Invalidate();
+			return oldState;
+		}
+	}
+}