Added N-dimensional sum of Gaussians GradMinimizer test
Added N-dimensional sum of Gaussians GradMinimizer test

roofit-dev/parallel-roofit-scripts,roofit-dev/parallel-roofit-scripts,roofit-dev/parallel-roofit-scripts,roofit-dev/parallel-roofit-scripts,roofit-dev/parallel-roofit-scripts