Add anonymization job

[ironjan]

• The old tool made lender, receiver, student, etc. anonymous 30d after the folders were returned
• The current tool does not
• It would be nice to have this
  • Instead of replacing the names with "arno nym" the names could be hashed
  • One reason for this would be to evaluate queries like "student x has lent a folder very long and someone seems to remember that this happened before"