Added a new type of stat manipulator value type, the "reponse curve". Pick the type of curve, and the value you want to modify the curve's response to where the current value of the stat is positioned in it's range. Can be used to modify the impact of a stat manipulator's value by what point of the stat's range the current value is at. (eg. eating a berry when you're really hungry feels more filling than when eating it on a full stomack).