akt password-set: change the wallet password

Usage: akt password-set [--new-passfile=PATH] [--new-password=ARG] [--new-passenv=NAME]
                        [--counter-range MIN:MAX]

  Changes an existing password with a new password.
  By default the PBKDF2 iteration counter is in range 500000..1000000.
  You can change this range by using the `--counter-range` option.
  High values provide best password protection at the expense of speed.
