Allow players to save progress, so they can come back later

[jschlot]

While in it's basic design, we can always come back, we end up with weird stats bugs.
For example you complete a story, then go back over it again, and can get double credits.
But we can't reset when you go over it, because our scores were computed in aggregate over each choice.

Either:
get scores from a selector like we used to, so it won't matter what the score was, because it's actively computed, or figure out of to force a recompute when we revisit stories, or figure out how to not let an episode be replayed.