Consolidate mpi/nompi bpwriter examples into single sources for each

[chuckatkins]

No description provided.

[chuckatkins]

@williamfgc I wasn't sure how to adjust the fortran examples since I don't think the ADIOS2_HAVE_* preprocesser definitions are exposed through the module. If you know of a good way to achieve a single source for the fortran example I'd welcome it.

[williamfgc]

@chuckatkins yes, I don't know of a good way since the Fortran 90 pre-processor is not a standard/portable thing (gfortran uses -cpp and ifort uses -fpp to turn it on), but I am not sure ADIOS2_HAVE_* is automatically exposed. We could always compile and run mpi and "no-mpi (but mpi linked)" code now (e.g. bpls). BTW, thanks for doing this.

[chuckatkins]

From what I've been able to find it seems that if the .F90 extension is used rather than .f90 then most Fortran compilers invoke fpp by convention. See updated commit.

[williamfgc]

@chuckatkins sounds great.