Multi-framework output

[philtweir]

Some use-cases may want/need to use different workflow engines at different levels. For instance, dask-multithreaded within a process and snakemake/nextflow for process-level orchestration. This would allow a single (e.g.) nextflow task to run its own dask workflow with shared memory. One use-case could be orchestrating a range of interdependent batch jobs.

It should be technically simple to implement a way of indicating a way of rendering different subworkflows to different frameworks - perhaps via a combination of task tags in code, and tag->renderer mapping in render settings.