SimHash Distributed Encoders (Scalar, Document) for Old NuPIC.

[brev]

SimHashing Encoders

• SimHash Distributed Scalar Encoder (SHaDSE), and,
• SimHash Distributed Document Encoder (SHaDDE)

For Old NuPIC. This PR may not be for actual merging, as NuPIC is currently frozen. But, this resource should help people get this code up and running as simply as possible.

• I would love any Code Reviews, as this is my first real Python project. Thanks.
• I'll also open a PR to put these Python files temporarily into NuPIC.cpp, until C++ version (next).
• I'll create C++ versions of these for Community NuPIC.cpp after that.

Scalar Encoder:

• HTM Community Discussion: https://discourse.numenta.org/t/new-simhash-distributed-scalar-encoder-shadse/5860
• Original Article: http://www.luxrota.com/articles/2019/04/18/simhash-distributed-scalar-encoder-for-htm.html

Document Encoder:

See Scalar Encoder links for lots of good details first.

• HTM Community Discussion: https://discourse.numenta.org/t/also-simhash-document-encoder/5893
• Original Article: http://www.luxrota.com/articles/2019/04/23/simhash-distributed-document-encoder-for-htm.html

[breznak]

@brev Thanks for publishing the code! I'll review this later, you might consider a PR to nupic.py and nupic.cpp where I'd accept the new code :+1: Also, please review https://github.com/htm-community/nupic.cpp/pull/278 https://github.com/htm-community/nupic.cpp/issues/258#issuecomment-466446149 for @ctrl-z-9000-times implemented RDSE using a hashing function (I have really only briefly looked at your code, but seems there might be some similarity?)

[brev]

Working on a version for nupic.cpp and nupic.py next, will link to it here when done.