rgw, cls_rgw: provide optional version id, versioned epoch to olh ops

rgw, cls_rgw: provide optional version id, versioned epoch to olh ops

Let system users specify optional params: rgwx-version-id,
rgwx-versioned-epoch. These will apply to object modification operations
(put object, copy object, delete object), and provide the mechanism that
the sync agent will use to apply remote object changes.
Copy operation hasn't been done yet.

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