Add conversion to and from Java primitives

[MateuszKubuszok]

• [x] conversions
• [x] test
• [x] documentation

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.98%. Comparing base (2e1a36f) to head (1708f36). Report is 115 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #556 +/- ## ========================================== + Coverage 87.75% 87.98% +0.23% ========================================== Files 137 138 +1 Lines 5455 5536 +81 Branches 455 466 +11 ========================================== + Hits 4787 4871 +84 + Misses 668 665 -3 ```

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