Added specialization of MPIDataType for bool

      inline static MPI_Datatype MPIDataType( const double* ) { return MPI_DOUBLE; };

      inline static MPI_Datatype MPIDataType( const long double* ) { return MPI_LONG_DOUBLE; };

      // TODO: How to deal with bool

      // TODO: tested with MPI_LOR and MPI_LAND, but there should probably be unit tests for all operations

      inline static MPI_Datatype MPIDataType( const bool* )

      {

         // sizeof(bool) is implementation-defined: https://stackoverflow.com/a/4897859

         static_assert( sizeof(bool) == 1, "The programmer did not count with systems where sizeof(bool) != 1." );

         return MPI_CHAR;

      };

      using Request = MPI_Request;

      using CommunicationGroup = MPI_Comm;