LBP test added and comments in boosting and trainer

xbob/boosting/core/boosting.py

xbob/boosting/core/gaussiantrainer.py

xbob/boosting/core/trainers.py

xbob/boosting/features/__init__.py

xbob/boosting/features/local_feature.py

xbob/boosting/scripts/mnist_multi.py

xbob/boosting/tests/test_dlbp_features.py

xbob/boosting/tests/test_lbp_features.py

xbob/boosting/tests/test_mlpb_features.py

xbob/boosting/tests/test_tlpb_features.py

xbob/boosting/tests/test_trainer_stump.py