message: Fix '--help' of stitching_detailed.py sample
  Fixes the help for `--features`, previously listed all possible values as default value.
  Also adds the default value to the help for two other arguments
diff: @@ -103,19 +103,19 @@ parser.add_argument(
  )
  parser.add_argument(
  '--features', action='store', default=list(FEATURES_FIND_CHOICES.keys())[0],
  - help="Type of features used for images matching. The default is '%s'." % FEATURES_FIND_CHOICES.keys(),
  + help="Type of features used for images matching. The default is '%s'." % list(FEATURES_FIND_CHOICES.keys())[0],
  choices=FEATURES_FIND_CHOICES.keys(),
  type=str, dest='features'
  )
  parser.add_argument(
  '--matcher', action='store', default='homography',
  - help="Matcher used for pairwise image matching.",
  + help="Matcher used for pairwise image matching. The default is 'homography'.",
  choices=('homography', 'affine'),
  type=str, dest='matcher'
  )
  parser.add_argument(
  '--estimator', action='store', default=list(ESTIMATOR_CHOICES.keys())[0],
  - help="Type of estimator used for transformation estimation.",
  + help="Type of estimator used for transformation estimation. The default is '%s'." % list(ESTIMATOR_CHOICES.keys())[0],
  choices=ESTIMATOR_CHOICES.keys(),
  type=str, dest='estimator'
  )
  