Add javadocs to web site

The web site does not contain the javadocs, This change is to add javadoc generation to the site assembly process.

This will involve some investigation as we have the main project with 2 modules and then the "doc" directory which is not an official module but still a child of the parent pom. This means that the parent pom will need to assemble the javadoc and the "doc" pom will need to copy that into a directory for deployment. In addition the doc site.xml will need to be updated to have a link to to the javadocs.