rationalize mpi config tuning
The tuning of mpi parameters is difficult to distinguish from regular configurations.
I would propose that we unify this with a common prefix or suffix.
My current tendency is with a prefix, to have nicely sorted items. The prefix
tune. looks nice to me, but
prefs. is probably better since it bears resemblance to
After the change, we could add in additional preference tuning for mpich, intelmpi etc. The optional files would then look like this: