Initial checkin of lysrdiff.

Initial checkin of the proof-of-concept scripts used to backup
some of the most important data on Lysator to sedesopim.

* fetch-backup-work: New script.  Define all backup tasks by quering
  auto_home on nema, and listing certain directories on stalingrad and
  uhumhummy.  As set up, this will find home directories, user www
  directories that use Apache (not Roxen), and CVS and SVN projects on
  the stalingrad server.  Note, however, that only a select few of the
  tasks are actually selected, due to the current disc shortage on
  sedesopim.

* backup-one-task: New script.  Run rdiff-backup to back up one task.

* backup-all: New script.  This script repeatedly calls
  backup-one-task for all defined tasks.