Temporary fix for studydocuments upload form

We have a mysterious bug with our studydocuments upload form which we could not fix in time. Therefore we should temporarily remove the automatic re-upload feature of the upload form and inform the user that they have to do so on their own.

For more information on the issue above, see #129.

This change also requires an additional proxy service on our server cluster so that the requests on https://amiv.ethz.ch/media are forwarded to the API. This is required so that the download attribute on links works as intended. The required proxy is already in place.

It might take some time until the new solution works properly after deployment as we have to change the service worker which might be cached for one hour.

Below a screenshot how the form will look like with this fix: