Ensured Move() overload properly functions

This is embarrassing, but it seems the basic `Move()` overload in `TopicRepositoryBase` doesn't refer to the more complete `Move()` overload, nor does it do so in any of the concrete implementations. As a result, it is effectively unimplemented, and won't persist any changes to the database.

This is fixed here by simply referring it to the more complete overload (which additionally accepts `sibling`).

This also exposes a bigger issue: Most of these `public` methods should be marked as `abstract` since they're not fully implemented, and just intended to provide common support. That breaks the public contract, though, so will need to wait for 5.0.0.

Author: JeremyCaney

OnTopic/Repositories/TopicRepositoryBase.cs

@@ -387,20 +387,7 @@ topic is ContentTypeDescriptor descriptor &&
     | METHOD: MOVE
     \-------------------------------------------------------------------------------------------------------------------------*/
     /// <inheritdoc />
-    public virtual void Move([ValidatedNotNull]Topic topic, [ValidatedNotNull]Topic target) {
-
-      /*------------------------------------------------------------------------------------------------------------------------
-      | Validate parameters
-      \-----------------------------------------------------------------------------------------------------------------------*/
-      Contract.Requires(target != topic);
-      Contract.Requires(topic, "The topic parameter must be specified.");
-      Contract.Requires(target, "The target parameter must be specified.");
-      if (topic.Parent != target) {
-        MoveEvent?.Invoke(this, new MoveEventArgs(topic, target));
-        topic.SetParent(target);
-      }
-
-    }
+    public virtual void Move([ValidatedNotNull]Topic topic, [ValidatedNotNull]Topic target) => Move(topic, target, null);
 
     /// <summary>
     ///   Interface method that supports moving a topic from one position to another.