Exportcsvtoinflux

1. Feat: Force add timestamp to tag, filed of influx, if the csv does not have the timestamp column;
2. Fix: Fix the csv new or not new check, if the --csv target is folder

Fix: Fix issue https://github.com/Bugazelle/export-csv-to-influx/issues/10

Fix Bug:
If some CSV cells have no value, failed to insert data into influx