WIP - Update to work with Trimeshpy 0.0.4

[frheault]

Quick description

Allows user to save the good old VTK/FIB format in MI-Brain, similar logic to Stanislas PR for legacy surfaces, now for tractograms.
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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

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

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Checklist

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

[codecov]

Codecov Report

Attention: Patch coverage is 35.71429% with 9 lines in your changes missing coverage. Please review.

Project coverage is 68.32%. Comparing base (4e7047d) to head (bc42b6d).
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1003      +/-   ##
==========================================
+ Coverage   68.24%   68.32%   +0.07%     
==========================================
  Files         419      420       +1     
  Lines       21391    21454      +63     
  Branches     3209     3217       +8     
==========================================
+ Hits        14599    14658      +59     
- Misses       5530     5534       +4     
  Partials     1262     1262              

Components	Coverage Δ
Scripts	69.26% <35.71%> (+0.05%)	⬆️
Library	66.96% <ø> (+0.10%)	⬆️