pearson distance is not the expected pearson distance

[lpatiny]

The implemented algorithm is

• https://en.wikipedia.org/wiki/Pearson%27s_chi-squared_test

Not obvious if the currently implemented pearson should stay in this package of move to the "stat" package (to be discussed ...)

And it should be

• https://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient#For_a_sample

This is also a similarity and should move of folder