16 Oct 2017: --recertify added

-((10 Aug 2018: ex-post announcement of this release for historical purposes))-

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Changes since 1.7.3:

• feat(co2p): The new option --recertify to co2dice project append allows to extend
  certification files for some vehile-family with new ones

  Note:
  The old declaration-files are ALWAYS retained in the history of "re-certified"
  projects. You may control whether they old files will be also visible in the
  new Dice-report or not.

  For the new dice-report to contain ALL files (and in in alphabetical-order),
  use different file names - otherwise, the old-files will be overwritten.
  In the later case, the old files will be visible only to those having access
  to the whole project, such as the TAAs after receiving the project's exported
  archive.

• fix(co2p): co2dice project commands were raising NPE exception when iterating
  existing dice tags, e.g. co2dice project export . to export only the current
  project raised::

  AttributeError: 'NoneType' object has no attribute 'startswith'
  

• fix(tstamp): co2dice tstamp were raising NPE exceptions when -force used on
  invalid signatures.