WIP

commit 78f171005391b928aaf1642b3206c534ed644332
Author: Matthew Ahrens <mahrens@delphix.com>
Date:   Wed Dec 11 14:33:41 2013 -0800

    4369 implement zfs bookmarks
    4368 zfs send filesystems from readonly pools
    Reviewed by: Christopher Siden <christopher.siden@delphix.com>
    Reviewed by: George Wilson <george.wilson@delphix.com>
    Approved by: Garrett D'Amore <garrett@damore.org>