Include global config parameters javadoc on myfaces-metadata using some myfaces builder plugin annotation

Actually we don't have a page with information about config params used on web.xml. It is not useful to maintain this in a separate page, because code continuously evolves and add new params or details.

In theory, these param are tied to a model id, so myfaces-api has ones, myfaces-impl has others ....... If we have this included on myfaces-metadata.xml, it is very easy to create a file with all this information when site generation is triggered.