[documentation] added an introduction to the core "XQuery Support in eXist-db" article.
- it's a long article, so I added a summary about each section to the intro.
- i noted that the article is advanced, so users who are new to eXist-db and to XQuery should turn elsewhere. in anticipation of receiving the FAQ article on "How can I learn more about XQuery and creating applications in eXist-db?", I have created a stub of the article, and added a link to this new document from the XQuery article.
- This article is excellent but needs a deep scrub to be updated for 2.0. Many tidbits seem to be circa 2007 (e.g. XQTS results cite a 2007 figure!) and from an earlier epoch of XQuery coding practices. At the very least, we should add mention here of (1) XQuery Update Syntax Status, (2) XQuery 3.0 Status. Thoughts on how to approach this?