Consider changing auto logodds_eps to reflect data size

[blucena]

Right now, when SplineCalib chooses logodds_eps automatically, it does so by looking at the smallest and largest values. However, perhaps it should also consider the size of the calibration set. For example, with 1,000 calibration points, it will be impossible to determine the difference between a 1 in 10,000 event and a 1 in 100,000 event. So perhaps, it should use a logodds_eps around .001 in this case. Still need to think about this...