Fix bug when not confirming Leave membership

Now, waiting for signals is way easier.

- Beware of python closure parameters in for loops !
- Use the bma_access.get directly in classes that needs
to be refreshed when getting the result, instead

Identities are now refreshing correctly

fixme : Revocation signature is wrong

The certification button "Ok" is renamed to "Not a member" if a certification
cannot be emited