Script dps math

[VincentBeaud]

Quick description

Replace scil_tractogram_add_dps.py for a more general version scil_tractogram_dps_math.py. This new script allows "add", "delete" and "export" operations on data-per-streamline.

Type of change

Check the relevant options.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] 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

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

Example: I want to extract the seeds from tractogram.trk. I use the following command line. scil_tractogram_dps_math tractogram.trk export --export_dps_key seeds --export_dps_file seeds.txt

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
• [x] 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

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

Project coverage is 69.44%. Comparing base (4d2715b) to head (5fa929c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1066 +/- ## ========================================== + Coverage 69.41% 69.44% +0.02% ========================================== Files 447 447 Lines 24046 24061 +15 Branches 3280 3285 +5 ========================================== + Hits 16691 16708 +17 + Misses 5960 5959 -1 + Partials 1395 1394 -1 ``` | [Components](https://app.codecov.io/gh/scilus/scilpy/pull/1066/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/1066/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `70.31% <100.00%> (+0.03%)` | :arrow_up: | | [Library](https://app.codecov.io/gh/scilus/scilpy/pull/1066/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scilus) | `68.27% <ø> (+0.01%)` | :arrow_up: |