Drop MPI1 usage

Compilation of Boost MPI using code fails with OpenMPI 4.0. For example:
```
[ 1%] Building CXX object src/core/cluster_analysis/CMakeFiles/cluster_analysis.dir/Cluster.cpp.o
cd /builddir/build/BUILD/espresso-4.0.0/openmpi_build/src/core/cluster_analysis && /usr/bin/c++ -DH5XX_USE_MPI -Dcluster_analysis_EXPORTS -I/builddir/build/BUILD/espresso-4.0.0/src -I/builddir/build/BUILD/espresso-4.0.0/openmpi_build/src -I/builddir/build/BUILD/espresso-4.0.0/src/core -I/builddir/build/BUILD/espresso-4.0.0/openmpi_build/src/core -isystem /usr/include/openmpi-x86_64 -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -pthread -Wall -Wno-sign-compare -Wno-unused-function -Wno-unused-variable -DNDEBUG -fPIC -std=c++11 -o CMakeFiles/cluster_analysis.dir/Cluster.cpp.o -c /builddir/build/BUILD/espresso-4.0.0/src/core/cluster_analysis/Cluster.cpp
BUILDSTDERR: In file included from /usr/include/boost/mpi/communicator.hpp:17:0,
BUILDSTDERR: from /builddir/build/BUILD/espresso-4.0.0/src/core/communication.hpp:56,
BUILDSTDERR: from /builddir/build/BUILD/espresso-4.0.0/src/core/grid.hpp:47,
BUILDSTDERR: from /builddir/build/BUILD/espresso-4.0.0/src/core/cluster_analysis/Cluster.cpp:19:
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp: In constructor 'boost::mpi::detail::mpi_datatype_primitive::mpi_datatype_primitive(const void*)':
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp:52:7: error: 'MPI_Address' was not declared in this scope
BUILDSTDERR: BOOST_MPI_CHECK_RESULT(MPI_Address,(const_cast(orig), &origin));
BUILDSTDERR: ^
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp: In member function 'ompi_datatype_t* boost::mpi::detail::mpi_datatype_primitive::get_mpi_datatype()':
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp:75:9: error: 'MPI_Type_struct' was not declared in this scope
BUILDSTDERR: BOOST_MPI_CHECK_RESULT(MPI_Type_struct,
BUILDSTDERR: ^
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp: In member function 'void boost::mpi::detail::mpi_datatype_primitive::save_impl(const void*, MPI_Datatype, int)':
BUILDSTDERR: /usr/include/boost/mpi/detail/mpi_datatype_primitive.hpp:108:7: error: 'MPI_Address' was not declared in this scope
BUILDSTDERR: BOOST_MPI_CHECK_RESULT(MPI_Address,(const_cast(p), &a));
BUILDSTDERR: ^
BUILDSTDERR: make[2]: *** [src/core/cluster_analysis/CMakeFiles/cluster_analysis.dir/Cluster.cpp.o] Error 1
```