[WIP] Add a (jaccard) similarity method to nodegraph and bitstorage

[luizirber]

• Is it mergeable?
• make test Did it pass the tests?
• make clean diff-cover If it introduces new functionality in
  scripts/ is it tested?
• make format diff_pylint_report cppcheck doc pydocstyle Is it well
  formatted?
• Did it change the command-line interface? Only backwards-compatible
  additions are allowed without a major version increment. Changing file
  formats also requires a major version number increment.
• For substantial changes or changes to the command-line interface, is it
  documented in CHANGELOG.md? See keepachangelog
  for more details.
• Was a spellchecker run on the source code and documentation after
  changes were made?
• Do the changes respect streaming IO? (Are they
  tested for streaming IO?)

[standage]

Let me see if I'm grokking this:

• bitwise AND --> buckets where both Bloom filters have 1
• bitwise OR --> buckets where either Bloom filter has 1
• __builtin_popcountll --> optimized function for counting buckets that satisfy the specified criteria

[luizirber]

__builtin_popcountll is a glorified count function to check how many bits are set to 1. A pure python equivalent would be

>>> a = 0b0101
>>> b = 0b1010
>>> bin(a & b).count('1')
0
>>> bin(a | b).count('1')
4