* Update `testMHFP.py` to check distance to self is zero
* Fix `MHFPEncoder::Distance` to compute a distance instead of a similarity
* Fix distance used for testing `MHFPEncoder::Distance` in `testMHFP.py`
* Fix expected distance values in `testMHFPFingerprint.cpp`
* Fix undeclared variable in `testMHFP.py`
* Fix C++ documentation of `MHFPEncoder::Distance` to mention Hamming instead of Jaccard distance