Report.java: added the report attributes start-time, start-date,
finish-time, and finish-date, removed elapsed detection time attribute.
Updated the Report factory method and constructor to receive two Date
objects (one representing the start time and the other representing the
end time). 

DetectionTask.java: (re)implemented the updated Report factory method by
passing a Date object encapsulating the detection-scan start date and
time and a Date object encapsulating the finish time.
Merge branch 'rework_report_times'