Intro screen scenario

@AmbientOSX, @ajiraffe, @BrettASwift, @scottnc27603 

I added the intro screen scenario, made it so that success doesn't have to have a popup, made it so that the scenario still advances when it doesn't, mucked around with the sounds that get played (and the names of the sounds that get played), hooked up a trigger that fires a VO when you add the first forward block in scenario 1, ... I think that's about it.

There's probably bits and pieces in there for all 4 of you to check out.
I think it would be clearer using an `||` with both `either` and the other option, but I guess that's just preferential.