Update yaml schema

[eyoung55]

Purpose

Add better explanations to the top-level categories in the yaml schema, add units to each option, and generally clean up the descriptions before the final tagging.

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

docs built locally and passing

Checklist

Put an x in the boxes that apply.

• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation

[eyoung55]

TODO:

• clean up descriptions
• add top-level descriptions to general, domain, etc.