I updated the download view and restrict it with the
`JobAuthorizationMixin`. I updated as well the link generated for the
files to download by removing the sha1 in the URL that isn't relevant
anymore. I deleted as well the `api/v1` from the url because the
datastore has no meaning to change location in the future therefore the
numerotation of the API in the url isn't necessary.

I deleted the `sha1file` function that isn't used anymore.

I updated the `urls.py` file accordingly.

Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>