Fix a few XML Comments

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.XamlDom/Project/DesignInstanceExtension.cs

@@ -6,6 +6,9 @@ using System.Windows.Markup;
 
 namespace ICSharpCode.WpfDesign.XamlDom
 {
+	/// <summary>
+	/// A class wich Implementes the DesignInstanceExtension normaly defined in the Blend Namespace
+	/// </summary>
 	public class DesignInstanceExtension : MarkupExtension
 	{
 		public DesignInstanceExtension(Type type)

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.XamlDom/Project/XamlXmlWriter.cs

@@ -12,7 +12,7 @@ using System.Xml;
 namespace ICSharpCode.WpfDesign.XamlDom
 {
 	/// <summary>
-	/// Description of XamlXmlWriter.
+	/// A special XamlXmlWriter wich fixes &amp; and &quot; in MarkupExtensions where not correctly handeled!
 	/// </summary>
 	public class XamlXmlWriter : XmlWriter
 	{