Support Eddie w/ --runmode=qsub & --platform=eddie

[kelly-sovacool]

Changes

• Add --platform argument to set platform explicitly. If not set, the platform is still detected automatically with scluster.
• Add qsub option for --runmode to support qsub in addition to slurm.
• Add draft profile for eddie (config/eddie).
• Improve how config templating works with envsubst.
• Explicitly export variables used globally in charlie.

Usage for Eddie:

charlie -w=/path/to/workdir --platform=eddie -m=init
charlie -w=/path/to/workdir --platform=eddie -m=qsub

Issues

resolves #134

PR Checklist

(Strikethrough any points that are not applicable.)

• This comment contains a description of changes with justifications, with any relevant issues linked.
• Update docs if there are any API changes.
• Update CHANGELOG.md with a short description of any user-facing changes and reference the PR number. Guidelines: https://keepachangelog.com/en/1.1.0/