메시지 클래스 새로 작성

hwe/sql/schema.sql

@@ -422,7 +422,6 @@ CREATE TABLE `message` (
 	`id` INT(11) NOT NULL AUTO_INCREMENT,
 	`mailbox` INT(11) NOT NULL COMMENT '9999 == public, >= 9000 national',
 	`type` ENUM('private','national','public','diplomacy') NOT NULL,
-	`is_sender` BIT(1) NOT NULL,
 	`src` INT(11) NOT NULL,
 	`dest` INT(11) NOT NULL,
 	`time` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,