rgw/logging: add support for GetBucketLogging and PutBucketLogging

rgw/logging: add support for GetBucketLogging and PutBucketLogging

this is based on AWS server access logs:
- https://docs.aws.amazon.com/AmazonS3/latest/userguide/enable-server-access-logging.html
- https://docs.aws.amazon.com/AmazonS3/latest/userguide/ServerLogs.html
- https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutBucketLogging.html
- https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetBucketLogging.html

however, a new mode was added called "journal" where:
- logs of PUT, COPY and MPU are guaranteed
- we have logs of DELETE and multi-DELETE operations (not guaranteed)
- log records hold only minimal amount of information

Fixes: https://tracker.ceph.com/issues/984
Signed-off-by: Yuval Lifshitz <ylifshit@redhat.com>