Par 23 par 24 par 25 move jdocbook style and version

PAR-23: move jdocbook style module to parents project
PAR-24: change version of jdocbook style plugin in doc-parent
PAR-25: style documentation: add white background

example at: http://dev.geomajas.org/PAR-23_PAR-24_PAR-25_styleDocumentation/