Unit tests dwi

[EmmaRenauld]

Quick description

Unit tests for the dwi files.

Changes:

• Now the dwi outlier detection takes into consideration the symmetry of b-vectors.
• In compute_dwi_attenuation: instead of dividing by 0 and then removing infinite values (which generates warning) the division by 0 is handled beforehand.

Type of change

Check the relevant options.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [x] Unit tests

Provide data, screenshots, command line to test (if relevant)

...

Checklist

• [x] My code follows the style guidelines of this project (run autopep8)
• [x] I added relevant citations to scripts, modules and functions docstrings and descriptions
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I moved all functions from the script file (except the argparser and main) to scilpy modules
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 72.09302% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 69.17%. Comparing base (bcf63aa) to head (73646bd). Report is 9 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #918 +/- ## ========================================== + Coverage 68.98% 69.17% +0.18% ========================================== Files 388 389 +1 Lines 20918 20963 +45 Branches 3220 3233 +13 ========================================== + Hits 14431 14501 +70 + Misses 5164 5132 -32 - Partials 1323 1330 +7 ``` | [Components](https://app.codecov.io/gh/scilus/scilpy/pull/918/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | Coverage Δ | | |---|---|---| | [Scripts](https://app.codecov.io/gh/scilus/scilpy/pull/918/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `71.60% <75.00%> (+0.11%)` | :arrow_up: | | [Library](https://app.codecov.io/gh/scilus/scilpy/pull/918/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `65.05% <71.79%> (+0.35%)` | :arrow_up: |