feat(urlrewrite): major rewrite

- Built on existing work by Wolfgang and others
- removed extra verbal padding for more concise document
- Re-ordered some of the more complex topics to the end of the document
- Re-factored headings for easier navigation from sidebar (e.g. controller XML model) and better internal linking
- Reviewed the eXist O'Reilly book content to ensure documentation parity
- Added some examples

Author: yamahito