CSerializeEnvelopeListener(sPath, iAtEvery)
  saves 
 CSerializeEnvelopeListener(sPath, iAtEvery, sBackingUp)
  saves a backup if sBackup ='backup' (creates one 2 files
  the last and the current step)
 CSerializeEnvelopeListener(sPath, [], fEveryZ)
  saves after pasing given distance or distances