Added dc() instead of count() when group-by field is present. Because count() doesn't do a distinct count in Splunk. Must be the dc() function instead.
Breaking change: Instead of feeding the output class with the results,
they are now returned as strings (*Backend.generate()) or list
(SigmaCollectionParser.generate()). Users of the library must now take
care of the output to the terminal, files or wherever Sigma rules should
be pushed to.