MATH-817
Algorithem for fitting of a multivariate normal distributions mixture
(implemented by Jared Becksfort).
Added "MixtureMultivariateNormalDistribution" class as "syntactic sugar".
Two unit tests are currently set to "@Ignore" (because they rely on "equals"
which the patch did not seem to implement "equals" consistently).


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1459382 13f79535-47bb-0310-9956-ffa450edef68