Documentation glossary added -- now let's go make it better :)

I've had a few requests for a glossary of terms to help people
understand things, for when the documentation explaining things down
the one golden path didn't quite succeed in explaning what it set out
to explain. I think that's valid, we can reinforce things by
explaining them in different ways.

So I wrote a glossary. This document is a start, just a start. Here
it is: http://ansible.cc/docs/glossary.html

Since all of our documentation lives in git (docsite/rst/glossary.rst)
I would welcome for anyone to improve it by adding more content,
crosslinks back into the documentation where things are being
discussed, etc.

Patches welcome for all kinds of things.

I'm going to work on the best practices page and making that better
tomorrow too (along with a handful of other features). Today was
mostly about merging a TON of pull requests. Lots of great stuff
lately.

--Michael