Use Docbkx Maven Plugin to build handbook

Here is a suggestion for simplifying handbook building using Docbkx Maven Plugin instead of manually applying DocBook XSLs with Ant. To the best of my knowledge, the documents produced remain unchanged.

A few related observations:
* Wouldn't packaging "pom" be better for handbook than "jar"?
* highlight.xsl does not seem to be in use? Should it be deleted?
* identity.xsl and generate-id.xsl seem to be of limited value. If the point is to generate sensible and stable anchor names then I think just hand-coding them would be better. If not, then why not rely on the anchors generated by DocBook? Am I missing something?