Provide documentation on parallel/distributed debugging

[Paul Hargrove]

We have noticed a lack of information on parallel/distributed debugging in debugging.md. All we say now is:

Note in particular that runs of multi-rank jobs on many systems include non-trivial spawning activities (e.g., required spawning scripts and/or fork calls) that serial debuggers generally won't correctly follow and handle. Hence the general recommendation to debug multi-rank jobs by attaching your favorite debugger to already-running rank processes.

We should be advising users to try the same tool(s) the apply to distributed MPI applications. However, that requires launch via mpi-spawner (which we need to figure out how to "spell" for the user).

Perhaps most importantly, we should test what we recommend on at least Cori or Summit (hopefully both).

[Dan Bonachea]

This was discussed in the 2020-02-12 meeting and deferred to next release milestone.

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Mass roll-over of open issues to next release milestone

[Dan Bonachea]

Clear past Milestone for open issues