[WIP] [FIX] Trying to fix MPI linking

CMakeLists.txt

src/CMakeLists.txt

src/DataSet/DataSet.cpp

src/ErrorFunction/ErrorFunctions.cpp

src/ErrorFunction/ErrorFunctions.h

src/LearningMethods/LazyLearning.cpp

src/LearningMethods/LevenbergMarquardt.cpp

src/LearningMethods/MultiGridLearning.cpp

src/LearningMethods/NormalizedGradientDescent.cpp

src/Network/NeuralNetwork.cpp

src/Reader/CSVReader.cpp

src/Reader/XYZReader.cpp

src/SymmetryFunction/ACSFParametersOptimizer.cpp

src/examples/CMakeLists.txt

src/examples/acsf.cpp

src/examples/dev_sandbox.cpp

src/mpi_wrapper.cpp

src/mpi_wrapper.h