This patch fixes some cases where the JATS writer was introducing
semantically significant whitespace by indenting and wrapping tags.
Note that the JATS spec has a content model for `<p>` tags of `(#PCDATA | ...`.
Any tag where `#PCDATA` children are possible should not have any
indentation. The same is true for `<th>`, `<td>`, `<term>`, `<label>`.