Fix some typos, broken links and other issues in extension docs

chrome/common/extensions/docs/templates/intros/cookies.html

 <h2 id="manifest">Manifest</h2>
 
 <p>To use the cookies API,
 you must declare the "cookies" permission in your manifest,
-along with <a href="manifest.html#permissions">host permissions</a>
+along with <a href="declare_permissions.html">host permissions</a>
 for any hosts whose cookies
 you want to access.
 For example:</p>
 
 <pre>{
   "name": "My extension",
   ...
   <b>"permissions": [
     "cookies",
     "*://*.google.com"
   ]</b>,
   ...
 }</pre>
 
 <h2 id="examples"> Examples </h2>
 
 <p>
 You can find a simple example
 of using the cookies API in the
 <a href="http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/api/cookies/">examples/api/cookies</a>
 directory.
 For other examples
 and for help in viewing the source code,
 see <a href="samples.html">Samples</a>.
-</p>
+</p>