Added DEPRECATED versions of statistic and variance in streaming MMD

DEPRECATED versions are available with

 - statistic type S_UNBIASED_DEPRECATED
 - null variance estimation method NO_PERMUTATION_DEPRECATED
 - null approximation method MMD1_GAUSSIAN_DEPRECATED
Hm, do not quite understand this. Does "DEPRECATED blockwise statistic computation" refer only to normalizing constants? NO_PERMUTATION_DEPRECATED refers to the old (incorrect) version of the variance/covariance computations - why is this different for kernel selection and for standard tests with a fixed kernel?