Handling multiple authentication types

Updates to close out #44. 

* Moving authenticators into CDI providers
* Updating login form tags to handle LDAP login better
* Adding moderator group function to LDAP auth
I see. So, changing it to request scope would make the `LDAPApi` simpler, right? (if we decide to also refactor).

Can you change to RequestScoped, then? I'm afraid it causes some awkward bug in the future. And you decide if you want to refactor `LDAPApi`, since it's your baby :)