Calcify internal data structures

[Lazula]

This project has outgrown widespread dict usage. They were very useful when this was a single-file script, but now I'm passing around dicts with expected forms, checking for key existence, using one massive dict to store everything, etc.

[Lazula]

PS: This includes using strings in place of enumerable constants

[Lazula]

Still not done until the API data dictionaries and CLI arguments are typed.