Write byline, dateline if relationships change

This is a somewhat debatable change. Positively, it will write a byline (`LastModified`) and dateline (`LastModifiedBy`) if only the relationships have changed, even if no attributes have changed, thus providing a more accurate record and, to a degree, improved auditing. Negatively, it will create phantom versions, since relationships aren't otherwise versioned; if a user rolls back to such a version, the relationships themselves won't be rolled back.

Author: JeremyCaney

OnTopic.Data.Sql/SqlTopicRepository.cs

@@ -340,7 +340,7 @@ SqlDateTime version
       var isNew                 = topic.Id == -1;
       var areReferencesResolved = true;
       var areRelationshipsDirty = topic.Relationships.IsDirty();
-      var areAttributesDirty    = topic.Attributes.IsDirty(excludeLastModified: true);
+      var areAttributesDirty    = topic.Attributes.IsDirty(excludeLastModified: !areRelationshipsDirty);
       var extendedAttributeList = GetAttributes(topic, isExtendedAttribute: true);
       var indexedAttributeList  = GetAttributes(
         topic                   : topic,