consider changing the action of `overwriteXLS` in `dataset.summary()`

[emilioxavier]

Hi Currently, the overwriteXLS option in the dataset.summary() function will cause the function to exit (stop) if the Excel workbook already exists. It would be better if the function

• checked if the Excel workbook existed
• warned if the Excel workbook exists and completes the function

Possible options could be

• If the option overwriteXLS is TRUE and the Excel workbook exists, then the Excel workbook is overwritten, and the user is informed.
• If the option overwriteXLS is FALSE, then the Excel workbook is not overwritten, and the user is informed.
• If the option overwriteXLS is FALSE and NO Excel workbook exists, then NO Excel workbook is written

Thank you Emilio