[FIX] fix and refactor demos, and update help sections

[Remi-Gau]

closes #565
closes #156

[codecov]

Codecov Report

Merging #701 (c537f9f) into main (3d248c7) will increase coverage by 0.03%.
The diff coverage is 62.10%.

@@            Coverage Diff             @@
##             main     #701      +/-   ##
==========================================
+ Coverage   76.05%   76.08%   +0.03%     
==========================================
  Files         212      214       +2     
  Lines        5450     5508      +58     
==========================================
+ Hits         4145     4191      +46     
- Misses       1305     1317      +12     

Flag	Coverage Δ
unittests	76.08% <62.10%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/IO/createDerivativeDir.m	100.00% <ø> (ø)
src/IO/getData.m	96.29% <ø> (ø)
src/IO/loadAndCheckOptions.m	92.00% <ø> (ø)
src/IO/saveOptions.m	100.00% <ø> (ø)
src/IO/unzipAndReturnsFullpathName.m	57.14% <ø> (ø)
src/QA/anatomicalQA.m	0.00% <ø> (ø)
src/QA/anatomicalQALesion.m	0.00% <ø> (ø)
src/QA/computeDesignEfficiency.m	55.38% <ø> (ø)
src/QA/functionalQA.m	0.00% <ø> (ø)
src/QA/mriqcQA.m	0.00% <ø> (ø)
... and 117 more

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