Separate command and job script interpolation.

[bschroeter]

Interpolation into the command and job script is (mostly) handled through additional kwargs into the submit function, however, with the addition of advanced directives I can see this quickly getting out of hand, particularly when a keyword argument that influences directives also conflicts with something that should be interpolated into the job script proper (i.e. storage).

Suggest having explicit dictionaries for command / job script arguments, OR leaving the directives as a dictionary that can also be accessed via jinja (inside the job script).

For example:

job_id = client.submit("job.sh", cargs=dict(), jargs=dict())

# ....OR something like

# assumed storage=["gdata/rp24", "scratch/rp23"]

# Maintain both a rendered and unrendered version
directives["storage"] = storage
directives_str = self._render_directives(directives)

# Add both to the interpolation context
context["directives"] = directives
context["directives_str"] = directives_str

I'll just leave this issue here for something to think about.