fishnet v2.0.0

• Updated to Stockfish 12 NNUE.
• Fishnet is now distributed as a standalone binary instead of a Python module.
  To update, uninstall fishnet 1.x (pip uninstall fishnet) and install the
  new version. You can keep using your fishnet.ini.
• Removed --threads-per-process. Analysis is now always single-threaded for
  reproducibility, parallelizing over positions instead. This also allows
  finishing games more quickly, instead of starting to analyse multiple games
  at the same time.
• Removed --memory. All clients will now use the same setting for
  reproducibility.
• Removed --stockfish-command and --engine-dir.
  Reproducible Stockfish builds
  for various CPU models now come bundled with the fishnet binary.
• Removed deprecated --fixed-backoff, --no-fixed-backoff,
  and --setoption.