LDAP: consolidate config prefix determination, autofill combo box in settings
LDAP: Clear cache on saving settings
LDAP: clean up, save configuration is now handled by Ajax
LDAP: improve and cleanup settings JS
LPAP: cleanup settings.php, it's already ajaxified
LDAP: add missing new LDAP Helper
LDAP: implement deleteConfiguration feature
LDAP: forgotten file for deleteConfig feature