Create mechanism for knowing if a Scene is queued or playing based on child clips.

[joslarson]

Create mechanism for knowing if a Scene is queued or playing based on child clips.

[joslarson]

I looked into wether it was possible to loop over all tracks and their clips using a track bank and a clipslot bank, but setting the position of the bank is asynchronous, so it's not so simple. Next things to try would be to see if we could make a wrapper for the banks using promises and async/await.