Delete images and csvs on download

[abfleishman]

After getting the workflow running, I have been impressed with the ease of training, reviewing, and retraining a model. I will add ideas here for improved flow.

on the tagging computer currently, we need to delete the csvs in the tag folder and the images and json in the tagging_location before running download_vott_json.py and beginning a new round of tagging. It would be nice for the files to be automatically deleted or maybe moved when running download_vott_json.py or at least an error that those files still exist and should be deleted prior to running the script.

[abfleishman]

I think this has been addressed @yashpande ?

[yashpande]

Looks like it.