XWIKI-12: Reorganize directory structure to match Maven2 best practices and cleanup build
XWIKI-12: Reorganize directory structure to match Maven2 best practices and cleanup build

* Added build-tools module to host tools for the build. Right now it's used to hold licenses and checkstyle rules.
* Note that we need to agree upon the checkstyle rules. Right now I have imported the rules from the Cargo project.

git-svn-id: 50c93b9c2d9041e46610830dd7836bad08be8b2e@1519 f329d543-caf0-0310-9063-dda96c69346f

pbondoer/xwiki-platform,xwiki/xwiki-platform,xwiki/xwiki-platform,pbondoer/xwiki-platform,pbondoer/xwiki-platform,xwiki/xwiki-platform,xwiki/xwiki-platform,xwiki/xwiki-platform,pbondoer/xwiki-platform,pbondoer/xwiki-platform