The possibility to configure an external duplicate has been removed from the views because no default external service integration exists. Reactivate later maybe..

Removed unnecessary log outputs
Wrong behaviour removed. If a valid prefilter exists but the filterpatternfields contain no value, the indexsearch got triggered nonetheless. The results which have been found on the base of the prefilter had been defined as duplicates which was wrong.
Code examples have been added to the important functions like ScanForDuplicates or RebuildDuplicatesCache