Finalizing the syntax

Finalizing the YAML syntax, for example:

---
amsthm:
  plain:    [Theorem]
  plain-unnumbered: [Lemma, Proposition, Corollary]
  definition:   [Definition,Conjecture,Example,Postulate,Problem]
  definition-unnumbered:    []
  remark:   [Case]
  remark-unnumbered:    [Remark,Note]
  proof:    [proof]
  parentcounter:    chapter
---

And the syntax to use an amsthm environment:

<div class="proof">
A Proof.
</div>
<div class="Theorem">
A Theorem.
</div>
<div class="Theorem boxed">
A boxed theorem if you define so in CSS. (Of course other filters needed if you want it boxed in LaTeX too.)
</div>