nrn_mpi wrappers can be a little more high-level and accept vectors instead of pointers

[ohm314]

Could the nrn_mpi wrappers be a little more high-level and accept vectors and hide the data-unwrapping .data() inside? Are they used inside modfile verbatims? If so then this is probably not an option (need to keep backward compat with neuron).

Originally posted by @ohm314 in #273

[nrnhines]

I can see some clarity benfits to having a corenrnmpi namespace with the wrappers you suggest.
One generally does not see mpi use in mod files (although i guess bin reporting is an exception)
One very useful functionality on the NEURON side of things is the possibility of
-DNRN_ENABLE_MPI_DYNAMIC=ON which means NEURON works on the user machine whether or not mpi has been installed.

[ohm314]

thanks @nrnhines ! that's good to know, then we have to tread carefully if there is a use case (bin reporting) for nrnmpi wrappers inside mod files. Anyway, I don't see this as a priority issue, just something to see how to improve in the future