Upsert monsterbook cards instead of delete -> insert

Also use existing connection during character saving for proper rollback.

database/sql/migration/monsterbook.sql

@@ -0,0 +1,4 @@
+ALTER TABLE cosmic.`monsterbook`
+CHANGE COLUMN `charid` `charid` INT(11) NOT NULL,
+ADD PRIMARY KEY (`charid`, `cardid`),
+ADD CONSTRAINT `FK_monsterbook_1` FOREIGN KEY (`charid`) REFERENCES `characters` (`id`) ON UPDATE CASCADE ON DELETE CASCADE;