nce matrix of the test distribution            [ D  x  D ]
%
% *Output arguments:*
%
%   M          mean of pred. distribution                            [ E  x  1 ]
%   S          covariance of the pred. distribution                  [ E  x  E ]
%   V          inv(s) times covariance between input and output      [ D  x  E ]
%   dMdm       output mean by input mean                             [ E  x  D ]
%   dSdm       output covariance by input mean                       [E*E x  D ]
%   dVdm       inv(s)*