QoL improvement - hero selector

Small change, but a big QoL improvement that removes a key point of frustration. 

 When you finish a heroes loop you can now choose which of the heroes to control in the next loop - so you can go straight to the one with the skills you need and, perhaps more importantly, if you mess up a heroes loop you can just re-run it without having to play the other three heroes first.

WebGL and all downloads updated with this change.