UI and UX problems on gest columns

• The `note` column is now on a single line (number + star)
• The `note` header is written in the same way as the others
• The `note` column is of no use to training managers as they already sort applications beforehand.
• As a trainer, we do not want to see the statut column.
  • Because if the application is:
    • Validated: it necessarily appears in the trainer view
    • Rejected: only visible to training managers
    • New: only visible to training managers
    • Invalid/incomplete: only visible to training managers

Closes #12 (closed),#16 (closed),#28 (closed),#38 (closed)