Should molecular formulas be Hill-ordered?

[mattwelborn]

Describe the bug
Molecular formulas (Molecule.get_molecular_formula) are currently alphabetically ordered. Should they be Hill ordered?

Additional context
This would require a data migration in Fractal.

Hill order: the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then the number of all other chemical elements subsequently, in alphabetical order of the chemical symbols. When the formula contains no carbon, all the elements, including hydrogen, are listed alphabetically.