reply to message stay if edited previous mess

Closes #142

See merge request !27

Resolve "survey questions: other languages known (multiselect?)"

Closes #148

See merge request !25

small correction in contribution.md

See merge request !26

Resolve "146-Failed to register a tutor"

See merge request !24

correction on surveys

See merge request !22

- TODO: Fix badly coded strings (no x.birthyear and x.birthyear.note -> causing problems in JSON)

Locales files
- fr.json
  - Changed informed consent for vocabulary test (only)
  - Minor spelling and phrasing fixes
  - Some automatic reordering (< i18n Ally on VSCode)
- en.json
  - Full automatic generation of keys based on fr.json
  - Full machine translation (< i18n Ally) of all keys
  - Manual revision (and correction) of a few dozen keys, but not yet all

Dev

See merge request !21

Resolve "tests: +sample item"

Closes #138

See merge request !17

Solve wrong avatar in chat and reply's arrow position

Closes #143 and #145

See merge request !20