[web] set proper Cache-Control header for static files - set Cache-Control max-age to match Expires - use the max_age method (defaults to 1 week) instead of hardcoded 6 months

[web] use a redirect for /data/foo requests that don't use the instance md5 hash The actual file contents can be cached for a long time. If the request doesn't use the hash, that's wrong. Using a redirect lets keep the caching for the actual file contents while not breaking requests missing the hash.