Cloning of backups, multi-partition backup disks, and more.

LYSrdiff partitions are now named after both the disk and the
partition, such as "2/0".  Support cloning.  Support watching the
backup activity remotely.  Various other fixes and improvements.

* lysrdiff-status: Adapted to the new disk/part scheme, and the new
  double "--" in state files.  Have a per-user state file, so that
  many users can use this script.

* lysrdiff-set-status.py: New.  Talk to lysrdiff-monitord.py.

* lysrdiff-move-obsolete: New option: --auto-confirm.  Adapted to the
  new disk/part scheme, and the new double "--" in state files.

* lysrdiff-move-job: New.  Move a job from one disk to another.
  (Actually, the old backup copy is left in place.  Use
  lysrdiff-move-obsolete to deal with it.)

* lysrdiff-monitord.py: New.  Keep track of what each disk is doing,
  and provide a vt100-over-telnet interface to watch it remotely.

* lysrdiff-label-disk: New.  Create the lysrdiff.id file and the basic
  directory structure.  Create space filler files that can be removed
  in an emergency.

* lysrdiff-df: New.  Run df on all mounted lysrdiff partitions.

* fetch-backup-work: Fetch all of lenin:/home.

* distribute-tasks: The lysrdiff argument is now on the form
  disk/part.

* Makefile
  (install): Added lysrdiff-label-disk and lysrdiff-df.
  (install-one-task): Added lysrdiff-set-status.py and
    lysrdiff-monitord.

* backup-one-task: Replaced the lysrdiffpart argument with disk and
  part arguments.  Handle --only-prune.  Log status using
  lysrdiff-set-status.py.  Removed special-case remoterdiff for
  sedesopim.  The parts of state file names are now separated by "--"
  intead of "-", to avoid confusion with categories and subcategories
  that contain a "-".  Remove increments older than 120 days.  Log the
  disk usage after a backup completes.  Clone the backup to all
  mounted copies.

* backup-all: Added --only-prune.  The part argument is now a
  disk/part string, and the format of the lysrdiff.id file has
  changed.