Updated table tests for latex writer changes.
Docx writer:  Use separate footnotes.xml for notes.

This seems to help LibreOffice convert the file, even though
it was valid docx before.

Note that the references in notes must be in
word/_rels/footnotes.xml.rel.  We handle this now by simply
making that file contain all the references in
word/_rels/document.xml.rel.  Something better could be done
eventually, but this works.

Closes #637.