Renamed all references: OpenMPI -> MPI

CMakeLists.txt

Core/CMakeLists.txt

Core/Simulation/MPISimulation.cpp

Core/Simulation/MPISimulation.h

Core/Simulation/Simulation.cpp

Core/Simulation/Simulation.h

Tests/Functional/Core/CMakeLists.txt

Tests/Functional/Core/MPI/mpitest.cpp

auto/Wrap/libBornAgainCore.py

auto/Wrap/libBornAgainCore_wrap.cpp

cmake/bornagain/modules/SearchInstalledSoftware.cmake

dev-tools/mpi/pytests/job1.cmd

dev-tools/mpi/pytests/mpi_cpp_test.py

dev-tools/mpi/pytests/mpi_test.py

dev-tools/mpi/pytests/version.py

dev-tools/mpi/supermuc.sh