gap analysis doc -- eliminate or drastically cut back last section

In a few days, I will need to tell people interested in our TPAC session
about the link and so anything other than fixing typos/grammatical errors
needs to come to an end.

In reading thru the doc, the final section "Other target applications of
MathML
<http://w3c.github.io/mathml-docs/gap-analysis/#other-target-applications-of-mathml>"
really seems out of place. I think we need to say something about
structured data/schema.org, but while the other topics in that section are
important, they have almost nothing to do with how to make expressions
speak appropriately, which is what the rest of the document focuses on.

I don't want to unilaterally drop the items in that section, so if you feel
they are relevant to the rest of the document, please state your reasons
for keeping them. Because time is critically short, this will be a one day
discussion -- Monday. If you have something to say about those sections pro
or con, say it now.

FYI: I've submitted some PRs that hopefully will get acted on Monday
morning that unify some of the earlier sections. Parallel markup still
needs the other examples and the text needs to get unified with the rest of
the document. I'm not the best person to do this, but if no one else steps
up to edit that section, you'll get stuck with what I come up with...

   Neil