Merge branch 'feature/reproductible-sums' into 'develop'

src/mesh/ItemArrayUtils.hpp

src/mesh/ItemValueUtils.hpp

src/mesh/SubItemArrayPerItemUtils.hpp

src/mesh/SubItemValuePerItemUtils.hpp

src/scheme/DiscreteFunctionP0.hpp

src/utils/Array.hpp

src/utils/CMakeLists.txt

src/utils/CommunicatorManager.cpp

src/utils/CommunicatorManager.hpp

src/utils/Messenger.cpp

src/utils/Messenger.hpp

src/utils/PETScWrapper.cpp

src/utils/Partitioner.cpp

src/utils/PugsUtils.cpp

src/utils/ReproducibleSumMPI.hpp

src/utils/ReproducibleSumManager.cpp

src/utils/ReproducibleSumManager.hpp

src/utils/ReproducibleSumUtils.hpp

tests/test_Array.cpp

tests/test_DiscreteFunctionP0.cpp