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>`.
This is now the default for pandoc's Markdown.
It allows whitespace between the two parts of a
reference link: e.g.
[a] [b]
[b]: url
This is now forbidden by default.
Closes#2602.
Modified template to include a `<back>` and `<body>` section.
This should give authors more flexibility, e.g. to put
acknowledgements metadata in `<back>`. References are
automatically extracted and put into `<back>`.
