Add a scrubber for the current game about joust

[beheh]

This is trivial with the game state scrubber. I'd also like actions marked on the bar, similar to the joust1 prototype.

[jleclanche]

I'd specifically like a turn marker of sorts, maybe of a different color depending on whose turn it is.

The UI I'm thinking is like, you have a progress bar which is green when it's the bottom player's turn and blue when it's the top player's turn. And when you drag the needle, you have a tooltip that says "Turn X".

[beheh]

Related to #3.

[beheh]

Playing, pausing, setting a variable speed and rewinding works. Working on the actual scrubber now.

[beheh]

Done. Tracking colored parts at #29.