Various code cleanups:

1. New style of package loading in f8b14aa
2. More robust checking if a symbol is an inverse-metric in 6604550
3. Using OptionsPattern[] in one place for future-proofing in 0f49024
4. Using trope of With[{CSh=CS[h]},...] for simpler code in 9adc0f3
5. Simpler/more robust way to determine maximum derivative order in 76d99f5