Calculates the root log-likelihood ratio for 2 state Datasets. See
#gDataSetsComparison(long[],long[]).
Given two events A and B, let k11 be the number of times both events
occur, k12 the incidence of B without A, k21 the count of A without B,
and k22 the number of times neither A nor B occurs. What is returned by
this method is
(sgn) sqrt(gValueDataSetsComparison({k11, k12}, {k21, k22})}
where
sgn is -1 if
k11 / (k11 + k12) < k21 / (k21 + k22));
1 otherwise.
Signed root LLR has two advantages over the basic LLR: a) it is positive
where k11 is bigger than expected, negative where it is lower b) if there
is no difference it is asymptotically normally distributed. This allows
one to talk about "number of standard deviations" which is a more common
frame of reference than the chi^2 distribution.