* Parse Markdown to support translation.
This upgrades from just splitting Markdown files on double-newlines, to
using a Markdown parser to break them into more appropriate chunks. The
upshot is that code samples are all in one message, lists are bundled
together, and generally it should be easier to translate.
* [WIP] helper to update po files for new translation
* process synthetic input file-by-file
* review comments
* remove temporary code
* fix msgfmt lints
I started using poedit to work on the translation, which has
reformatted large parts of the file, so the change is a lot larger
than just the newly translated parts.
