* Add uploads:sync_s3_acls rake task to ensure the ACLs in S3 are the correct (public-read or private) setting based on upload security
* Improved uploads:disable_secure_media to be more efficient and provide better messages to the user.
* Rename uploads:ensure_correct_acl task to uploads:secure_upload_analyse_and_update as it does more than check the ACL
* Many improvements to uploads:secure_upload_analyse_and_update
* Make sure that upload.access_control_post is unscoped so deleted posts are still fetched, because they still affect the security of the upload.
* Add escape hatch for capture_stdout in the form of RAILS_ENABLE_TEST_STDOUT. If provided the capture_stdout code will be ignored, so you can see the output if you need.
* Attachments (non media files) were being marked as secure if just
SiteSetting.prevent_anons_from_downloading_files was enabled. this
was not correct as nothing should be marked as actually "secure" in
the DB without that site setting enabled
* Also add a proper standalone spec file for the upload security class
