#46 Improve implementation of DoNotReindex

[Jean Jordaan]

Once a field has been marked "Add to index", then naturally items from all other fields with the same name will be cataloged under the same index.
So the "Add to index" toggle is not simply per-field. Even if it has not been set for a field, it should indicated that the index exists and field items will be cataloged.

Similarly, if an index already exists and I check "Add to index" on a field with the same id, then no database refresh should be triggered, as the database is already up to date.