Handle stale job items

Let's suppose there are some network issues or an eTranslation outage after an API call is made and eTranslation never calls back for that string. The job item will remain "in progress" (JobItemInterface::STATE_ACTIVE) forever in the case of continuous jobs. This is because, on cron, continuous are only sending for translation item that are in the inactive state (JobItemInterface::STATE_INACTIVE). We need a way to mark that job item as aborted if a reasonable amount of time has passed after it entered "in progress" state. For me six hours seem to be a decent amount to wait for a translation.