Fix the diff viewer and marker issues

[MaryConti]

We have seen cases were excel files and word files don't read correctly.  We have seen where an excel file is not properly read and large portions of the file are unavailable in the diff viewer.  We have seen where markers are disappearing -- the little flag is still there, but when you try to see the issue and discussion, there is an empty window.  Please fix these things.

[MaryConti]

Currently, I have a review of a word doc with 6 versions uploaded.  After one upload, the markers move to a different section of the doc and stay there for later versions.  The doc has had a number of smaller changes, but nothing significant in the areas where the markers are wrong, except whitespace.  The markers after that seem to be OK, too.

[MrDubya]

On the Excel item, all formatting is removed when viewing in the diff viewer, so I'm wondering if that's what you're referring to, or if that's possibly a symptom.  If so, there is a separate request to preserve Excel formatting in the Collaborator diff viewer which can be found here.