Build Lister: order_by default value set to date_scheduled

CLI build lister order defaults to date scheduled.
I've been debating in my head for like an hour, sigh, about whether this should be `date_scheduled` or `created_at`.  I'm leaning towards recommending `created_at`.  The primary reason would be that Unstartable builds do not have a `date_scheduled` so would sort very wrong.  However, it seems like most people would indeed really care more about `date_scheduled` but we almost never create a build and then do not (attempt to) start it.