Ceph

This will include:

• create(size, order, features)
• get_info(image)
• get_snapc
• snap_add * later snap_add_begin, snap_add_abort, snap_add_finish
• snap_remove * even later snap_remove_begin, snap_remove_abort, snap_remove_finish
• snap_list
• child_list
• set_ro * later maybe begin, abort, finish?
• set_rw
• set_parent
• remove_parent (after copy-up is done)
• set_child
• remove_child
• has_child