add HCE dev guide

        <ul>

          <li><a href="<?cs var:toroot ?>guide/topics/connectivity/nfc/nfc.html">NFC Basics</a></li>

          <li><a href="<?cs var:toroot ?>guide/topics/connectivity/nfc/advanced-nfc.html">Advanced NFC</a></li>

          <li><a href="<?cs var:toroot ?>guide/topics/connectivity/nfc/hce.html">Host-based Card Emulation</a></li>

        </ul>

      </li>

      <li><a href="<?cs var:toroot?>guide/topics/connectivity/wifip2p.html">

  framework APIs are based around a <a href="http://www.nfc-forum.org/">NFC Forum</a> standard

  called NDEF (NFC Data Exchange Format).</p>

<p>Android-powered devices with NFC simultaneously support three main modes of operation:</p>

<ol>

<li><strong>Reader/writer mode</strong>, allowing the NFC device to read and/or write 

passive NFC tags and stickers.</li>

<li><strong>P2P mode</strong>, allowing the NFC device to exchange data with other NFC 

peers; this operation mode is used by Android Beam.</li>

<li><strong>Card emulation mode</strong>, allowing the NFC device itself to act as an NFC 

card. The emulated NFC card can then be accessed by an external NFC reader, 

such as an NFC point-of-sale terminal.</li>

</ol>

  <dl>

    <dt><strong><a href="{@docRoot}guide/topics/connectivity/nfc/nfc.html">NFC Basics</a></strong></dt>

    <dd>This document describes how Android handles discovered NFC tags and how it notifies

    bytes using your own protocol stack. In these cases, Android provides support to detect

    certain tag technologies and to open communication with the tag using your own protocol

    stack.</dd>

    <dt><strong><a href="{@docRoot}guide/topics/connectivity/nfc/hce.html">Host-based Card Emulation</a></strong></dt>

    <dd>This document describes how Android devices can perform as NFC cards without using

    a secure element, allowing any Android application to emulate a card and talk directly to

    the NFC reader.</dd>

  </dl>

</p>