Document most core interfaces

Oqtane.Shared/Interfaces/IAuditable.cs

@@ -1,12 +1,30 @@
-using System;
+using System;
 
 namespace Oqtane.Models
 {
+    /// <summary>
+    /// Basic create/edit information - used in many objects. 
+    /// </summary>
     public interface IAuditable
     {
+        /// <summary>
+        /// Username of the creator of this Object.
+        /// </summary>
         string CreatedBy { get; set; }
+
+        /// <summary>
+        /// Created Timestamp for this Object.
+        /// </summary>
         DateTime CreatedOn { get; set; }
+        
+        /// <summary>
+        /// Username of the last user who modified this Object.
+        /// </summary>
         string ModifiedBy { get; set; }
+
+        /// <summary>
+        /// Modified Timestamp for this Object.
+        /// </summary>
         DateTime ModifiedOn { get; set; }
     }
 }