add support for tracking scheduler details
this allows us to record what processes are scheduled when and see them as marks, per CPU.
this was requested when using/looking at sysprof data and wasn't terribly difficult to implement, so landing a bit late to fill our some of our 45 feature set.
we will want to improve on how we draw marks though by allowing us to specify tagging colors per .name
field so things look a bit more like kernel shark.