rgw: metadata rm

Still needs to fix the way we remove user entries; need to take
different path, similar to put_entry())

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
cls_rgw, rgw: bucket index logs modifications

Add a log to the bucket index.

This commit also ties the "epoch" version that is kept
per index entry to the relevant ceph pool id. This fixes
the dependency on the specific pool where the object was
created, and makes it possible to copy rgw data pools.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
cls_rgw: bucket index versioning

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
radosgw-admin, cls_rgw: list bucket index log

a new radosgw-admin command to list bucket index log.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
radosgw-admin: bilog list gets marker and max-entries params

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>