Increase testing coverage

[jkrasting]

This is a thread to discussing strategies for increasing the testing coverage of the MDTF code. This is in advance of the "beta 3" release, but a broader issue that needs to be addressed.

Specifically, we need:

1. rapid, commit-level or PR testing of

• framework installation
• code flow of the PODs
• checks for broken links
• code quality (security, formatting)
• documentation generation

2. more through scientific and workflow vetting

• tests on other GFDL and NCAR experiments
• tests on different model resolutions
• tests on different data naming conventions (DRS vs. internal NCAR/GFDL formats)