Now you can edit a saved state file even if you forgot to grab
a dumpxml file prior to saving a domain.  Plus, in-place editing
feels so much nicer.

* tools/virsh.c (cmdSaveImageDumpxml, cmdSaveImageDefine)
(cmdSaveImageEdit): New commands.
* tools/virsh.pod (save-image-dumpxml, save-image-define)
(save-image-edit): Document them.