* Deprecate `--strip-empty-paragraphs` option. Instead we now
use an `empty_paragraphs` extension that can be enabled on
the reader or writer. By default, disabled.
* Add `Ext_empty_paragraphs` constructor to `Extension`.
* Revert "Docx reader: don't strip out empty paragraphs."
This reverts commit d6c58eb836.
* Implement `empty_paragraphs` extension in docx reader and writer,
opendocument writer, html reader and writer.
* Add tests for `empty_paragraphs` extension.
We now have the `--strip-empty-paragraphs` option for that,
if you want it. Closes#2252.
Updated docx reader tests.
We use stripEmptyParagraphs to avoid changing too
many tests. We should add new tests for empty paragraphs.
