GitLab

Remove reference to rails in README. Mainly by replacing 'rails' with 'django'. Also add the need of the redis contenair.

- 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).

- remove the HasSignedTosMixin and to the verifications in
  AllgoAccessMixin instead (along with email verification)
- add Tos.get_latest() and User.has_agreed_tos
- ignore ToS agreement if the db has no ToS entries

(this is a legal document, we should avoid juggling with multiple
 variants)

I added a mixin that checks if the user has accepted the latest ToS
version. If not the user is redirected to the ToS validation view. Once
accepted the user is redirected to the page he asked first.

I updated all the `login required` views by adding this new mixin.
One major issue of this code that the redirection argument passed to the
ToS validation view is the url name which is not a good practice I
think. A better case would to use the path but I wasn't able to write
the right regex in the url dispatcher.

Another issue is that the user won't be redirected at login or sign up
to the ToS validation view. This should be handled in the `adapter.py`
file.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>