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>`.
Support writing <fig> and <table-wrap> elements with <title> and
<caption> inside them by using Divs with class set to on of
fig, table-wrap or cation. The title is included as a Heading
so the constraint on where Heading can occur is also relaxed.
Also leaves out empty alt attributes on links.
