fix: don't call MPI_Comm_dup  on null communicator
fix: check null communicator in adios_open and adios_close
fix: duplicated comm introduced in 679cc9203ff: MPI communicator passed in adios_open
is valid only until adios_close. adios_finalize needs to use a communicator saved in
adios_init
Added simple domain decompostion generation, various refactoring
Merge branch 'master' of https://github.com/ornladios/ADIOS
(1) used uint64_t for dataspaces/dimes bounding box; (2) added the option 'enable_collective_read_meta' for dataspaces/dimes read method: one process fetches meta data and broadcasts to other processes; (3) updated dimension ordering;
using new DataSpaces put/get APIs that ADIOS can specify the global dimension information for variable