More backups, to separate partitions.

LYSrdiff can now backup up to separate partitions, creates more state
timestamp files, randomizes the backup order, and backs up most user
data.

* fetch-backup-work: Fetch all lsvn, lyscvs, lyswww and home tasks,
  not just a select few.  Fetch roxen tasks.

* backup-all: New arguments: a list of lysrdiffpart partitions to run.
  Check that the correct filesystems are mounted before doing
  anything.

* backup-one-task: New argument: lysrdiffpart.  That argument
  specifies which lysrdiff partition that the backup should be stored
  on.  It is a small integer.  Adjusted the paths to handle it.  Skip
  manhattan, since it is (temporarily) dead.  Store state information
  in a separate directory, and touch flag files for when a backup
  starts and ends, fails and is being attempted.

* distribute-tasks: New script.  This script is responsible for
  assigning new tasks to lysrdiff partitions.  It also randomizes the
  order of the tasks, to make the backup more fair.