OpenXML: DOCX corruption in files with deletion change tracking

[Chase Tingley]

At least, I think the cause is the change tracking marker. Roundtripping the attached file through the openxml filter will cause word/document.xml to become truncated after the paragraph containing the timecode.

[Chase Tingley]

Fix Issue 458, Fix Issue 467, and Fix Issue 473 in the openxml filter

This rewrites OpenXMLContentFilter.combineRepeatedFormat() and
splits out the markup simplification content to a new class called
ParagraphSimplifier.  This fixes many issues in the old code with
multiple <t> elements in a single run, as well as issues with tabs
and linebreaks that were being lost when interspersed with text.
This covers Issue 458 and re-fixes Issue 467 in a better way.

Additional fixes were to Issue 473 and an unfiled problem with
entities in deleted text that weren't being re-escaped in target
output.

This has caused some changes to placeholder creation in segments.

→ <<cset 2445b887857a>>