XWATCH-99 Embed XWatch GWT code in a zip in the generated wiki xar

* Introduce a maven plugin that loads a document from XML, can attach a file to it and write it back to XML. The plugin can also set 
XWiki object String properties.

* Renamed module "web" in "gwt". The gwt module doesn't depend on enterprise-web war anymore, and is packaged as a zip. The generated 
zip is dynamically attached to WatchCode.GWT with the fore-mentionned mojo when building watch wiki.



git-svn-id: https://svn.xwiki.org/svnroot/xwiki/xwiki-products/xwiki-watch/trunk/tools/build-doc-plugin@7285 f329d543-caf0-0310-9063-dda96c69346f