Better download progress (percent, content length, url).


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@632 024a02f7-42f7-40fc-9f58-65666d1f2450
Better download failure handling (resume, retry).


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@633 024a02f7-42f7-40fc-9f58-65666d1f2450