ST. LOUIS — One of the underrated things that Doug Armstrong brings to the table as the Blues’ general manager is an ability to space out expiring contracts. That’s not an easy task in this era of free agency and the salary cap. Give an assist here to assistant GM Ryan Miller, who does much of the heavy lifting when it comes to numbers crunching. So as the Blues’ enter the offseason, they have eight of their top nine forwards under contract for at least next season. It’s 11 of their top 13 if you want to extend it down the roster. On defense, it’s six of their top eight. That’s an impressive r…