libcephfs: add pool id/size lookup interface

Adds new interfaces ceph_get_pool_id() and ceph_get_pool_replication()
to libcephfs.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
java: support get pool id/replication interface

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Merge remote-tracking branch 'gh/wip-client-pool-api'

Reviewed-by: Sage Weil <sage@inktank.com>