Add Preview to templates-sdk develop nav and global nav in templates-sdk-dev. Remove dependence on -includePreview.

Change-Id: I1456c3c94522f58c7d1c899ff96dd95cdc6ada7c
diff --git a/tools/droiddoc/templates-sdk-dev/components/masthead.cs b/tools/droiddoc/templates-sdk-dev/components/masthead.cs
index d857ffb..b105b52 100644
--- a/tools/droiddoc/templates-sdk-dev/components/masthead.cs
+++ b/tools/droiddoc/templates-sdk-dev/components/masthead.cs
@@ -261,6 +261,9 @@
             </li>
           </ul>
         </li>
+        <li class="dac-nav-item preview">
+          <a class="dac-nav-link" href="<?cs var:toroot ?>preview/index.html">Preview</a>
+        </li>
         </ul>
       </div>
     </div>