Incorrect bankroll calculation when playing multiple spots

[mhluska]

We currently use amountEarned / handsPlayed to calculate expectation per hand and use bankroll variance to estimate variance per hand. This works well when playing only one hand the entire session but breaks down when multiple spots are played.

It might be better to calculate expectation per hand not empirically. But then we'll need to precompute count distributions for the various deck counts and penetrations and also precompute a baseline house advantage for each game type.