If the target symbolic link already existed, an invalid link in target
was created to java/target. Fixed by checking if the link exists before
creating it
Change-Id: If0ab57bfd8989f7c9d0facd8d1e8b9aaa98bc578
Also, download and build common directly instead of hacking the
build to use the jars from tarballs.openstack.org
Update the README.md to explain the new StackForge build
Change-Id: I08cc1b304eaad38fc0619a09efc91c11e8633199