Rewrite history page

sql/history.sql

@@ -3,7 +3,7 @@ create table history
     id INTEGER
         primary key autoincrement,
     set_id INTEGER not null references decks on delete cascade,
-    stat_id INTEGER not null references states on delete cascade,
+    word_id INTEGER not null references words on delete cascade,
     timestamp INTEGER not null,
     answer INTEGER not null,
     before INTEGER not null,