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
Do we need this `if`? The reason for this is just that `email` class? Maybe you could do something like:
```jsp
<c:set var="extraClass" value="${env.supports('feature.auth.db')? 'email' : ''}" />
<input ... class="... ${extraClass}" ..>
```