Fix save_data -> write_data changes; Updated docs

bob/bio/vein/algorithms/HammingDistance.py

bob/bio/vein/extractors/LocalBinaryPatterns.py

bob/bio/vein/extractors/MaximumCurvature.py

bob/bio/vein/extractors/NormalisedCrossCorrelation.py

bob/bio/vein/extractors/PrincipalCurvature.py

bob/bio/vein/extractors/RepeatedLineTracking.py

bob/bio/vein/extractors/WideLineDetector.py

bob/bio/vein/preprocessors/FingerCrop.py

doc/api.rst

doc/baselines.rst

doc/links.rst

doc/references.rst