alert for DBF removal when re-running a metric

[debboutr]

If the user has created a metric and needs to change something in the raster or elsewhere the user will have to delete both the .csv files AND the .DBF files in the AllocationandAccumulation folder. Create a flag or warning to alert the user that there are existing CSV/DBF in their respective location. If the user has deleted the CSVs and not the DBF's they may come up with the same error, which is why I'm writing this bug