add get_features script

get_features script is a wrapper for ./extract for training purpose.
It takes positive samples directory, negative samples directory and
the feature name as input. Output will be the pos_nr, neg_nr, and
the feature vectors of all the images inside those two directories.

Signed-off-by: Guangyu Sun <guangyu.sun@oracle.com>
support svm training

Add main class Trainer. It takes a feature file generated by
./get_features and train an svm model.

Signed-off-by: Guangyu Sun <guangyu.sun@oracle.com>
support svm predicting

Add class Predictor. It must read the model built by the trainer
before doing any prediction. It takes stdin as input with the same
format ./extract outputs. We can just pipe it in the main function.

Signed-off-by: Guangyu Sun <guangyu.sun@oracle.com>