That functor layer was there to delay the initialization of
authentication, but now that authentication has been moved out of
Web_election, it is no longer needed.

 - there is now a single Eliom reference holding the logged in user
 - per-election authentication is no longer handled by a submodule of
   WEB_ELECTION
 - the database of passwords for password authentication can only be
   initialized for the site from the configuration file

They were largely unused and untested.

We suppose any logged in user can vote; in preparation of a future
drop of the ACL system.