optimized hamming distance computation

[taras-sereda]

This PR optimizes computation of hamming distance by XORing two integers and counting bits. On folder with 4000 images allows to compute all pair-wise distances 30x faster then current implementation.

Attention: bit_count() was added in python 3.10
for earlier python version an equivalent helper function will serve the same purpose:

def big_count(n):
    count = 0
    while n:
        count += n & 1
        n >>= 1
    return count