Added gii model generator support read column comment to attribute label 

```
Example

Field      Type              Comment
id         int(11)unsinged   null
email      varchar(50)       电子邮件
password   varchar(50)       密码

public function attributeLabels() {
    return array(
        'id' => 'ID',
        'email' => '电子邮件',
        'password' => '密码',
    );
}
```