XTOOLS-3: Add new XWiki configuration resources module to share XWiki configuration files between build modules

* Added factorization of xwiki.cfg and upgraded to use latest Maven Assembly plugin version as the ones we were using had some issue with file permissions...

git-svn-id: https://svn.xwiki.org/svnroot/xwiki/xwiki-platform/xwiki-tools/trunk@3873 f329d543-caf0-0310-9063-dda96c69346f