Add a development environment for the flask backend

[ctmbl]

I just squash and rebase my branch form #86 (still not merged) and then update it to adapt it to a flask backend, just like I did for #88 I also fixed an issue 9480d75 I didn't saw in #88, anyway this was a first shot, not a definitive prod environment. However this PR should do as a definitive development environment, modulo some new commits in #86 post b0ab27d

[ctmbl]

No worries we can wait for tonight!

[atxr]

All clear then! :racehorse: