Ensure that implicitly dirty attributes are Save()d

Previously, the `SqlTopicRepository.Save()` would save an otherwise clean `Topic` if any of its `Attributes` were marked as indexed, even though their corresponding `AttributeDescriptor` marked them as extended. That is correct behavior. The opposite scenario, however, was not being tripped. As a result, attributes reconfigured from extended to indexed storage would not be picked up as part of `Save()` unless the `Topic` was _explicitly_ marked as `IsDirty()`. This fixes that issue, and resolves #73.

OnTopic.Data.Sql/SqlTopicRepository.cs

@@ -373,7 +373,10 @@ bool persistRelationships
       | current command. A more aggressive version of this would wrap much of the below logic in this, but this is just meant
       | as a quick fix to reduce the overhead of recursive saves.
       \-----------------------------------------------------------------------------------------------------------------------*/
-      areAttributesDirty        = areAttributesDirty || extendedAttributeList.Any(a => a.IsExtendedAttribute == false);
+      areAttributesDirty        =
+        areAttributesDirty      ||
+        indexedAttributeList.Any(a => a.IsExtendedAttribute == true) ||
+        extendedAttributeList.Any(a => a.IsExtendedAttribute == false);
 
       var isDirty               =
         isTopicDirty            ||