Slightly more efficient fully-connected layer

[m-usama-z]

Hi. I suggest changing the following piece of code in the reach_star_single_input function of the FullyConnectedLayer.m class

                V(1, 1, :, in_image.numPred + 1) = zeros(obj.OutputSize, 1, 'like', in_image.V);
                for i=1:n+1
                    I = in_image.V(:,:,:,i);
                    I = reshape(I,N,1); % flatten input
                    if i==1
                        V(1, 1,:,i) = obj.Weights*I + obj.Bias;
                    else
                        V(1, 1,:,i) = obj.Weights*I;
                    end
                end

to this:

                V(1, 1, :, :) = obj.Weights*reshape(in_image.V, N, n + 1);
                V(1, 1, :, 1) = reshape(V(1, 1, :, 1), obj.OutputSize, 1) + obj.Bias;

in order to improve efficiency for a large number of generators, for both cpu and gpu modes.

[mldiego]

Added this implementation in #243