  array of widths of the cost (summed together)
%     .expl         (optional) exploration parameter
%     .angle        (optional) array of angle indices
%     .target       target state                                    [D x  1 ]
%   m               mean of state distribution                      [D x  1 ]
%   s               covariance matrix for the state distribution    [D x  D ]
%
% *Output arguments:*
%
%   L     expected cost                                             [1 x  1 ]
%   dLdm  derivativ