[pvr] mark current playing item as selected if no selected item exists

This re-adds the functionality to the PVR windows that the current playing item is selected with the alteration that we do it only if no previous selection exists.

@Jalle19 it's not as easy to sync the selected item between channel and guide window because the guide grid control is different from a normal view control.

I also want to discuss the behavior as it's differ a little from what we have before.