* 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.
The secure media functionality relied on `SiteSetting.enable_s3_uploads?` which, as we found in dev, did not take into account global S3 settings via `GlobalSetting.use_s3?`. We now use `SiteSetting.Upload.enable_s3_uploads` instead to be more consistent.
Also, we now validate `enable_s3_uploads` changes, because if `GlobalSetting.use_s3?` is true users should NOT be enabling S3 uploads manually.
Martin Brennan
Martin Brennan