Recover cache headers for stored items

[neutralino1]

PR #623 attempted to add cache headers to the following endpoints:

1. GET /api/v1/storage/<namespace>/<key>/data which redirects to the actual stored payload location (storage plug-in-dependent)
2. S3 pre-signed URLs
3. GET /api/v1/storage/<namespace>/<key>/local which is LocalStorage's payload download's endpoint (redirected to from /data)

The first two ones are risky as they make the assumption that both responses are cached at the same time, and will expire at the same time. PR #652 removes these headers until further analysis (this issue).