update barcheck tool to test against known final elevations.

A useful QC method is to modify a bar check so that we have proper elevations on a bar or plate taken from a GNSS rover or we get elevations on the concrete pad at a boat ramp. Would be great if we could input in an elevation into the bar check tool ,define an area of the swath and compute a 30s average of the elevations within the defined area and then generate a report for comparison. This test the entire survey system. Pictures attached for further clarification. Usually comparison is done in MBMAX