[dlib] feature normalisation

// declares a matrix with 2 rows and 1 column
typedef dlib::matrix<double, 2, 1> sample_type;
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(some middle operations)
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// here's how to declare a normalizer in dlib
dlib::vector_normalizer<sample_type> normalizer;

// let the normalizer learn the mean and standard deviation of the samples
normalizer.train(samples);

// now normalize each sample
for (unsigned long i = 0; i < samples.size(); ++i)
    samples[i] = normalizer(samples[i]);