S3 storage option to not set ACLs

[zerocrates]

Current Amazon guidance is to do everything with bucket policies and not do per-object ACLs. The current S3 code always tries to set an ACL when putting an object which causes issues unless a bucket is specifically set back to the old style.

An option that disables ACL selection would be a useful improvement for the S3 setup: though it will need a docs note that if enabled, public/privateness of the objects in the bucket is entirely up to the S3 configuration, even if "timeout" and presigned URLs are enabled.