Upgrade old MD5 password hashing (#822)

database/tables.sql

@@ -115,6 +115,7 @@ CREATE TABLE `ospos_employees` (
   `password` varchar(255) NOT NULL,
   `person_id` int(10) NOT NULL,
   `deleted` int(1) NOT NULL DEFAULT '0',
+  `hash_version` int(1) NOT NULL DEFAULT '2'
   UNIQUE KEY `username` (`username`),
   KEY `person_id` (`person_id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;