Standardise date and filename formats in reports from part 2, 4, 5, and 6

[jhmigueles]

Date format is provided as "%Y-%m-%d %H:%M:%S" in part 2 reports, "%d/%m/%Y" in part 4 reports, and "%Y-%m-%d" in part 5 reports.

Filnames are provided including the ".RData" extension in some reports and without it in others.

It would be good to standardise the formatting of these two columns in the reports to facilitate merging in postprocessing (if needed).