- fixed both SQL files
 - fixed `list_pms()`
 - fixed `delete_pm()`
 - updated CHANGELOG
 - added abilty to send `system` PM's for `send_pm()` & `send_pms()`
 - changed `name` to `username` in aauth_users table
 - changed `name` to `username` in all user related functions
 - changed `$name` to `$username` in `create_user()` & `update_user()`
 - added `user_exist_by_username()`
 - changed `user_exist_by_name()` to an alias of `user_exist_by_username()`