[FEATURE] Synchronicity between merlin allocations and workflow computing resources

[srcopela]

I'm just getting started with Merlin and noticed that there are a few steps that need to be coordinated properly and it might be nice if there were utilities in Merlin to support that coordination.

Specifically, when I submit my merlin job to a parallel compute resource (e.g. via a slurm script as described in https://merlin.readthedocs.io/en/latest/merlin_commands.html), I specify the number of compute nodes. Then, within my merlin workflow, I specify the number of "nodes" for my workers in the workers sub-block of the merlin block (e.g. number of workers). Then I also specify the number of nodes and processors for each sample directly using the cmd: keyword in a step defined in the study block.

A utility to generate an sbatch file from a merlin spec would help keep things sorted, it seems like there's enough information contained there to do such a thing.

Also, as a novice to celery, I found the nodes keyword in the workers block to be somewhat misleading - it seems to control the number of workers, but my first instinct was that it was some kind of 'node allocation' assigned to the worker. Particularly if you're working with multi-node tasks, I can see others making the same mistake.