Offer to replace export if it exists, refs #11082
Offer to replace export if it exists, refs #11082

The CSV term usage export was appending rows if exporting to an existng
CSV file. Added log to, if the CSV export file already exists, ask the user
if they want to replace it (aborting if they decide not to).

artefactual/atom,artefactual/atom,artefactual/atom