HG variable death rates

[CampbellCrowley]

Games lengths often vary a large amount, causing death rate probabilities to change each day could possibly help to control the length of each game.

Allowing users to choose a starting deathRateProbabilities and then probabilities on a certain day, would allow the values to be interpolated (and possibly extrapolated if the game continues past the end date, but likely keeping the values constant after the final day is preferable)