* commit '21111c2cddff2a62b2de0afe9e70607cc4054e54': cherrypick Change-Id: Icf0c7772901f742c36ba417e07cc5e299f72849a fix broken links, update the dev guide intro, and update sitemap file
* commit '21111c2cddff2a62b2de0afe9e70607cc4054e54': cherrypick Change-Id: Icf0c7772901f742c36ba417e07cc5e299f72849a fix broken links, update the dev guide intro, and update sitemap file