add sitemap generator which outputs all public pages and also includes an ISitemap interface for modules

Oqtane.Shared/Models/Sitemap.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace Oqtane.Models
+{
+    /// <summary>
+    /// Describes a Sitemap
+    /// </summary>
+    public class Sitemap
+    {
+        /// <summary>
+        /// Url
+        /// </summary>
+        public string Url { get; set; }
+
+        /// <summary>
+        /// Url
+        /// </summary>
+        public DateTime ModifiedOn { get; set; }
+    }
+}