fast_job_submission: add new guide

[chu11]

Add new guide to improve job submission speed in Flux. I was on and off writing this for a bit, finally decided to write it for real.

Note, for now I just stuck this stupidly under "jobs" set of docs. I'm pretty sure its not the right place.

Possibly a "guide" section under tutorials? Ehhh?

[chu11]

re-pushed, I decided to put the tutorial under a new "how to" section of tutorials. The idea is that the "how to" topics will likely involve multiple commands or multiple prior topics, used together to describe something.

[vsoch]

@chu11 I think (my preference) for the time being since we have an entire jobs section would be to keep the tutorial under there, and when it's warranted to re-organized we think of all the pages in this section in that context. We are also working on the Command tutorials section, and I think it's going to get too watered down to start with "Howto" and "Commands." Arguably, everything is a "How to" and it's a category that moreso reflects we don't know exactly where to put it (and I'm going to suggest the well-established Jobs section for now).

[chu11]

yeah, i feel its a little bit in between the two. But lets go with the jobs section for now, moved it back.

[chu11]

rebased and re-pushed, "sub-instance" -> "subinstance"

[vsoch]

I think this tutorial is great and I don't see any issues, however I'm not experienced with this kind of submission.

[chu11]

re-pushed, cut and pasted code-block:: sh in some places where it should be code-block:: console`.

[chu11]

I think this tutorial is great and I don't see any issues, however I'm not experienced with this kind of submission.

Perhaps @grondo or @garlick could take a quick skim, make sure what I'm writing sounds good.

[SteVwonder]

Very nice!

[SteVwonder]

Suggested change

	The first mechanism is the ``--cc`` (carbon copy) roption in ``flux mini submit``. It will allow the user to replicate every id specified in an :ref:`IDSET<idset>`. Along with the ``{cc}`` substitution string, we can submit all 1000 scripts on the command line like so:
	The first mechanism is the ``--cc`` (carbon copy) option in ``flux mini submit``. It will allow the user to replicate every id specified in an :ref:`IDSET<idset>`. Along with the ``{cc}`` substitution string, we can submit all 1000 scripts on the command line like so:

[chu11]

re-pushed, with comment fixes from above and removing "flux mini" references