Added DEPRECATED versions of statistic and variance in streaming MMD

DEPRECATED versions are available with

 - statistic type S_INCOMPLETE_DEPRECATED
 - null variance estimation method NO_PERMUTATION_DEPRECATED
 - null approximation method MMD1_GAUSSIAN_DEPRECATED
Added graphical example for B-test
Merge pull request #2349 from lambday/feature/btest

Added DEPRECATED versions of statistic and variance in streaming MMD