Numerous configuration and syntax enhancements

Summary of changes:

* Reworked the convert.sh script to allow the formats to be specified (defaults to html,docbook,fopdf)
* Configured image paths so previews work when viewing / rendering an individual chapter
* Put the UI macros to use (keybinding, button and menu) (requires setting the `experimental` attribute)
* Demo the use of open block as a content container (like a div) to simplify lists with complex content
* Remove unnecessary option="header" attribute on tables (Asciidoctor works it out by convention)
* Configure syntax highlighting
* Additional minor cleanups, grammar and spelling corrections

Best practices regarding images:

* You should not hardcode the path to the image. Instead, the image path should be relative to the "image catalog", which can be configured on a per-document or per-build basis.
* Titles for block (standalone) images should be specified above the macro