Allow setting LDAP bind and pass via Admin UI

Ldap settings set in XWiki Preferences override those set in xwiki.cfg. If so - it should be pretty simple to have separate directories to subwikis. Setting global LDAP parameters in xwiki.cfg and specific ldap server, bind DN, bind password, base DN and group mapping could be enough to have subwikis with users from different AD servers.

Am I right, that all we need for that is to add xwiki.authentication.ldap.bind_DN and xwiki.authentication.ldap.bind_pass to the UI ?