related to #156
it would great to have the possibility to query about the progress, something such as:

case class WarcFileReport(file: File, started: Boolean, finished: Boolean, completed: Double)

def progressFn(warcFileReports: List[WarcFileReport]) {
  warcFileReports.foreach(println)
}

RecordLoader.loadArchives(file, sc, progressFnEvery = 1 hour, progressFn)
.foreach(archiveRecord => println(s"+++ ${archiveRecord.getUrl}"))

Is something like that feasible?