Topic/plat 6723

The method getModifiedCurvatureMatrix in NonLinearLeastSquare and NonLinearLeastSquareWithPenalty was slow because it computed J^T * J (where J is the Jacobian matrix) directly calling the getEntry method of DoubleMatrix2D. We now have a dedicated method in MatrixAlgebra that works directly on double arrays.
There is a method that takes sigmas and one that does not - setting sigma to 1.0 is the same as removing it from the calculation, which is the behaviour we want