change name of offline doc tab to "API reference"

      <li class="dac-nav-item develop">

        <a class="dac-nav-link has-subnav" href="/reference/packages.html" zh-tw-lang="參考資源" 

        zh-cn-lang="参考" ru-lang="Справочник" ko-lang="참조문서" ja-lang="リファレンス" 

        es-lang="Referencia">Android <?cs var:sdk.version ?>&nbsp;r<?cs var:sdk.rel.id ?></a>

        es-lang="Referencia">API Reference</a>

      <div class="dac-nav-secondary develop">

        <h1 style="font-size: 20px; line-height: 24px; margin: 20px; color:#444"

          >Android <?cs var:sdk.version ?> r<?cs var:sdk.rel.id ?>

        </h1>

      </div>

      </li>

    </ul>

  </nav>