v0.5: Merge pull request #100 from thomas-vincent/fix_for_release

• Add a safeguard when motion correction is producing negative values: warn and use offset.
• adapt to removal of field .samples in bst event structure (see brainstorm-tools/brainstorm3#199)
• Full GLM pipeline almost completed (still WIP):
  • import/export of manual markings (bad channel tagging, events) outside of bst DB
  • template-based using Colin27 or subject-specific anatomy
  • cortical projection using MNE and optical model
  • precoloring 1st level GLM
  • MFX 2nd level GLM contrasts
  • Computation of group-level masks, that can work with an atlas (ROI-based results)
  • Documentation available here: https://github.com/Nirstorm/nirstorm/wiki/%5BWIP%5D-GLM-pipeline:-surface-and-template-based
• tested with brainstorm v3.190521 (still need to test with latest brainstorm for final release)