Flake8 F errors and several bug fixes

bob/bio/vein/algorithm/MiuraMatch.py

bob/bio/vein/config/maximum_curvature.py

bob/bio/vein/config/principal_curvature.py

bob/bio/vein/config/repeated_line_tracking.py

bob/bio/vein/config/wide_line_detector.py

bob/bio/vein/database/fv3d.py

bob/bio/vein/database/verafinger.py

bob/bio/vein/extractor/MaximumCurvature.py

bob/bio/vein/extractor/NormalisedCrossCorrelation.py

bob/bio/vein/extractor/PrincipalCurvature.py

bob/bio/vein/extractor/__init__.py

bob/bio/vein/preprocessor/crop.py

bob/bio/vein/preprocessor/filters.py

bob/bio/vein/preprocessor/mask.py

bob/bio/vein/preprocessor/preprocessor.py

bob/bio/vein/script/blame.py

bob/bio/vein/script/compare_rois.py

bob/bio/vein/script/validate.py

bob/bio/vein/script/view_sample.py

bob/bio/vein/tests/test_tools.py