Enable the use of label descriptions of language codes in the UI & publishing workflows

Appears to be a github GIST for this at: https://gist.github.com/jrnk/8eb57b065ea0b098d571 . Would ideally use both the codes & labels in the submission workflows but labels only in the MD record displays.

Start with the linked GitHub Gist, then trace the UI and publishing workflows that handle language codes and the Markdown record displays. Done means submission workflows show both codes and labels, while Markdown records show labels only; the issue names no files or tests to run.

Written by the indexing model from the issue text.