Added denied phrases for usernames

This feature allow to disallow users with banned pharses to join the bot
if they are not vouched.
Database Insertion command:
INSERT INTO  `ghost`.`oh_custom_fields` (`field_id` ,`field_name`
,`field_value`)VALUES ('1',  'oh_bannednamepartials',  'hitler heil
gadafi grief neub' );
Seperation should be done via space.