added `login_with_name` config item
renamed `aauth_error_login_failed` to `aauth_error_login_failed_email` in lang file
added `aauth_error_login_failed_name` in lang file
changed in login function `$email` to `$identifier`
Modified lang-file constants to include prefix. This will help avoid collisions.
Also added a few missing items to the lang-file.
Modified list_user_var_keys() to return an array so that it can be looped through.
Fixed duplicate message when sending password reset email, line 424.
modified: application/language/english/aauth_lang.php
modified: application/libraries/Aauth.php