[WIP] Simplify and fix one-hot encoding

[kristofgazso]

The library currently seems to be working with floats for one-hot encoding, and was also using for for loops for it, which is not very parallelizable

This doesn't seem usual, since categorical data points should normally be represented as ints as opposed to floats, as they can be expected to be used as indices

One test is still failing: test_point_counter_iris, maybe because of some weird float use. The final assert in the test seems shows that something is wrong:

old poisoned 120 not_poisoned 120 correctly_defended 54 incorrectly_defended 3 original_points_total 120 training_points_total 183 new poisoned 281 not_poisoned -41 correctly_defended 240 incorrectly_defended 0 original_points_total 120 training_points_total 181 

would be cool if the devs took a look =))