Refactor to just be a parser & transform

Refactor to just be a parser & transform

As opposed to sitting on top of ⛩📰 书社, restricting codex webpages
to basically not containing anything else, 🪾📰 Caudex now (more
simply) just provides a parser and transform which can be used _with_
⛩📰 书社, assuming a properly set up installation. This is more
complicated to configure properly (you can¦t just clone the repo and
do a `make +category` to get started anymore), but it enables codices
to be created and included in other websites, which is really
necessary (and also provides much more flexibility with controlling the
output).

Some areas where the code was too opinionated have been loosened, and
the implementation has been simplified into (1) parsing Les·M·L parse
results into R·D·F, and (2) transforming that R·D·F into codex pages.

The checksum digits have changed to `+!@=U` as these are the only
options which work with both ⛩📰 书社 and U·R·N syntaxes.