Generalized frameworks for GCM ingestion and stellar grids

What's Changed

• More flexible grid framework by @tedjohnson12 in #34
• Generalize the GCM ingestion framework by @tedjohnson12 in #38
• Merge for v0.5.0 by @tedjohnson12 in #39

Full Changelog: v0.4.1...v0.5.0