Update analysis_slurm.py code for smoother analyses on Expanse

[bfhealy]

This PR adjusts analysis_slurm.py to facilitate smoother analyses with Expanse:

• The structure of directories and files created by analysis_slurm.py is modified, with the slurm script saved directly in the nmma directory.
• More environment variables serve as wildcards for inputs specified by the user on SkyPortal (TMIN, TMAX, and DT).
• The --outdir argument is adjusted to create a subdirectory labeled by each source's ID and analysis start time.
• A test is added to tests/analysis.py to test slurm script generation.

[mcoughlin]

LGTM

[mcoughlin]

@bfhealy feel free to merge once tests pass

[sahiljhawar]

Tests failing!

analysis_slurm.main() is called without any arguments, even without slurm specific arguments!? Also I think args in test_analysis should be global so that test_analysis args’ can be accessed by test_analysis_slurm().

[sahiljhawar]

@mcoughlin I don't know about rebasing and dont want to mess up. Can you please merge this?