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

this had the bad effect of making all links/buttons disapper
when clicked

(now that allgo supports multiple e-mail addresses per user, they
 can resolve the problem without the admins)

Resolve "CGU validation"

Closes #279

See merge request !146

Resolve "Merge WebappForm with UserWebappForm"

Closes #273

See merge request !145

because the decimal format is kind of messy, especially we have:
1.01 != 1.1 and 1.1 == 1.10

Tos.version is now a CharField. For ordering, we use Tos.id instead
(the latest tos is the one with highest id).