Accepted, Unscheduled Sessions should include Schedule Items

When using the Room/Timeslot Scheduler, the "Accepted, Unscheduled Sessions" list doesn't include Schedule Items. We'd expect this so that we can more easily schedule all things happening for our event from one place. We were also expecting this list to be provided via a View Block so that if this were the intended functionality that we could customize it to our particular needs.

On way to accomplish the fix would be to adjust cod_schedule_get_unscheduled_sessions() to include schedule items in its select query. It may be, however, that there are more broad reasons for separating logic between "items" and "sessions".