Core/RBAC: Add .reload rbac command and prevent possible crash if rbac_permissions has wrong data

sql/updates/world/2013_02_27_00_world_command.sql

@@ -0,0 +1,3 @@
+DELETE FROM `command` WHERE `name` = 'reload rbac';
+INSERT INTO `command` (`name`,`security`,`help`) VALUES
+('reload rbac',3,'Syntax: .reload rbac\nReload rbac system.');