Banks generator: do not ignore optional fields
We currently ignore optional fields.
For the Caisse d'Épargne pro for example the nuser
field is mandatory. The Caisse d'Épargne does not require it though.
We should stop ignoring the optional fields but mark them as optional so that the UI can specify it. If not set by the user the default value should be used.
See https://git.weboob.org/weboob/weboob/blob/master/modules/caissedepargne/module.py#L56
Edited by Nicolas Frandeboeuf