Add option to disable SMTP auth

Closes #61

SQL/mysql.initial.sql

@@ -32,6 +32,10 @@ CREATE TABLE IF NOT EXISTS `ident_switch`
 	`smtp_port`
 		int
 		CHECK(`smtp_port` > 0 AND `smtp_port` <= 65535),
+	`smtp_auth`
+        smallint
+        NOT NULL
+        DEFAULT 1,
 	`drafts_mbox`
 		varchar(64),
 	`sent_mbox`