Implement Configurate-style `OptionSource`

Configurate currently has a very basic option system, I'd like to integrate that system into `option` since its goals are pretty similar.

See https://github.com/SpongePowered/Configurate/blob/ab9abae78fb64e2e8ef25f407cd37a65f99aeba5/core/src/main/java/org/spongepowered/configurate/loader/LoaderOptionSource.java#L40