Extend the ArcFileReportGenerator to handle WARC files

This generator is activated when the setting XX is enabled. So to test this, we need to use a deploy_configuration with this enabled. To test that it works equally with ARC or WARC as the Heritrix archiveformat. Deploy netarchivesuite in ARC mode or WARC mode, and test that the contents of the reports is consistent with the arc or warc files actually harvested. The reports can be downloaded from the Browse reports for jobs on the Harveststatus-jobdetails.jsp page. And the list of the actually harvested files can be shown from the "Browse harvest files for job" on the Harveststatus-jobdetails.jsp page