[dataimport] dict.iteritems() → dict.items()

[dataimport] use next builtin instead of next method on iterators

[dataimport] import StringIO from io

[dataimport] backport massive store from dataio cube Some tweaks have been made to work with 3.21 foreign key constraints. Also test are not executed in our own pg cluster instead of polluting the system one. Closes #5414760

[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.

[web] fix typo in doc string

[web] stop adding an Expires header with all responses As per RFC 1945 (HTTP 1.0): If the date given is equal to or earlier than the value of the Date header, the recipient must not cache the enclosed entity. As per RFC 7234 (HTTP 1.1 Caching): If a response includes a Cache-Control field with the max-age directive (Section 5.2.2.8), a recipient MUST ignore the Expires field. Bottom line, the Expires header is now handled wherever the Cache-Control is handled: inside cache managers.