dvc remove unused files locally and remotely

https://github.com/iterative/dvc/issues/1019

`dvc add dir_name` (update local cache)
`dvc push dir_name` (push to remote dvc)
`git add dir_name.dvc` (add to git)
`git commit -m "message"` (commit to git)   
`git push` (push to remote git)

git pull
dvc pull

We suggest using Python 3.8 or above for DVC. There seems to be an issue with Python 3.7 and DVC: https://stackoverflow.com/questions/75194771/dvc-data-version-control-error-importerror-cannot-import-name-fsspec-loop