fix precision and recall calculations

[cmmartin]

Fixes #323

Checklist

• My branch is up-to-date with development branch.
• Everything works and tested on latest stable Rust.
• Coverage and Linting have been applied

Current behaviour

• recall
  • binary case calculates precision instead of recall due to incorrect false negative counting
  • multiclass case computes accuracy (total correct / total) instead of macro-averaged recall
• precision
  • binary case calculates recall instead of precision due to incorrect false positive counting
  • multiclass case computes accuracy instead of macro-averaged precision

New expected behaviour

• recall
  • binary case correctly calculates recall
  • multiclass case computes macro-averaged recall instead of accuracy
  • handles zero-division edge case
• precision
  • binary case correctly calculates precision
  • multiclass case computes macro-averaged precision instead of accuracy
  • handles zero-division edge case

Change logs

[Mec-iS]

thanks a lot. I will review this on monday