More documentation - almost all Models done

https://github.com/oqtane/oqtane.framework/issues/1382
Should not contain any code changes, just docs

Oqtane.Shared/Models/Culture.cs

@@ -1,11 +1,26 @@
 namespace Oqtane.Models
 {
+    /// <summary>
+    /// Culture information describing a Culture
+    /// </summary>
     public class Culture
     {
+        /// <summary>
+        /// Short code like `en` or `en-US`
+        /// </summary>
         public string Name { get; set; }
 
+        /// <summary>
+        /// Nice name for the user, like `English (United States)`
+        /// </summary>
         public string DisplayName { get; set; }
 
+        /// <summary>
+        /// Information if this is the default culture. 
+        /// </summary>
+        /// <remarks>
+        /// Not sure if this is actually valid, as ATM there is no setting to configure a _default_ culture
+        /// </remarks>
         public bool IsDefault { get; set; }
     }
 }