Update cs1.lua to upstream version

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I took a quick look at merging in updates to the cs1.lua module from upstream (https://en.wikipedia.org/wiki/Module:Citation/CS1), but it seems like things have evolved pretty dramatically. Eg, helper routines (like for identifiers) have been split off into sub-modules.

Not sure how important the updates are... some new features include better pre-print support (?), and more identifiers. I'm not very familiar with this sort of code (Lua wiki templates), and the current behavior of wikiciteparser "works for me", so probably won't take a stab at this myself, but opening the issue for visibility.