XWIKI-5518: Introduce Extension Manager XAEXTENSION-1: Initial implementation
XWIKI-5518: Introduce Extension Manager
XAEXTENSION-1: Initial implementation

git-svn-id: 04343649e741710b2e0f622af6defd1ac33e5ca5@31277 f329d543-caf0-0310-9063-dda96c69346f

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