Previously `<section>` tags were just parsed as raw HTML
blocks. With this change, section elements are parsed as
Div elements with the class "section". The HTML writer will
use `<section>` tags to render these Divs in HTML5; otherwise
they will be rendered as `<div class="section">`.
Closes#2438.
Renamed some tests, introducing subsidiary directories
for fb2, docx, epub.
Cleaned up tests in cabal file.
Combined dokuwiki-writer and dokuwiki_inline_formatting tests.
