PROV-811 access check fix
NOJIRA Allow set administrator who is not system administrator to switch between set groups in set list widget

Previously you could in theory administrate all sets as user with
action ‘can_administrate_sets’ but there was no way to navigate to
others’ sets without the ‘is_administrator’ action.
NOJIRA Announce attachment file size via HTTP header in binary download views

This way the browser knows how big the file actually is and can show
percentage, time left, etc. It’s also very useful if the HTTP responses
are handled by something like a reverse proxy. We’ve seen cases where
the proxy would actually refuse to relay the response when this wasn’t
set.
Merge remote-tracking branch 'upstream/master'