Removing .env and data files before launching bootstrap.

Closes #320

See merge request !174

Ci pylint

See merge request !165

dev-toolbox added to the container list in bootstrap script.

Closes #307

See merge request !167

I assume the runner will have docker and docker-compose installed.
/!\ gitlab-runner has to be a sudoer, without asking for password. /!\

The build is only the call to ./bootstrap.
The tests are done with pylint3 (can fail) and the 'test' (for unit and functionnal tests).
And to terminate, cleanning is always done. This is required because otherwise bootstrap will try to erase previous data without being sudoer, and this will fail.

Also to reduce the creation of files created by "root", we do not generate python cache files for the controller.

Note that pylint will store its metrics in the metrics directory, through the PYLINTHOME env variable.

The command to launch "from outside":
docker exec -i dev-django pylint3 --rcfile=.pylintrc allgo

Add django extension to generate the class diagram of the models

See merge request !159

Revert "Merge branch 'test_update' into 'django'"

See merge request !158

This reverts merge request !157

Test update

See merge request !157

Resolve "(discrete) error on fresh install when click on "jobs""

Closes #291

See merge request !156

- remove duplicated code
- remove the "Edit the application properties" button (not useful,
  because it is a very rare operation and also because the sandbox
  panel is no longer accessible from this page)
- reword "Finish the configuration of your app" as "There is an
  active sandbox" (which is much clearer)
- fix the condition for displaying the sandbox button

context switches must not happen within a sqlalchemy transaction

for two reasons:
- it is no longer a concern since email addresses are well verified now
- it was broken (an entry would be created in auth_user anyway,
  whereas the other tables would not be updated)
- it was doubly broken (raise PermissionError on first gitlab login too)

UI : two suggestions for the user

See merge request !153

Initial django migration

Closes #259

See merge request !154