Show Builder: Allow rearranging traffic items that are scheduled at the same time.

some users like to re-arrange things in the trackpad so they can line up their playlists ahead of time, this includes wanting to re-arrage traffic items, which isn't possible if traffic items are scheduled at the same time.

Let's make it possible to rearrange traffic items that are scheduled at the same time. You still should not be able to rearrange them so they fall out of order based on their scheduled time.