Move Bitmessage to peer-to-peer RTC. Move I2P-Bote to Self contained networks. Remove "email alternatives" page. (#1559)

- Move I2P-Bote to Self contained networks.
- Remove "email alternatives" page and nav item

_includes/sections/instant-messenger.html

@@ -196,4 +196,5 @@
 <ul>
     <li><a href="https://status.im">Status.im</a> - Encrypted instant messenger with an integrated <a href="https://en.wikipedia.org/wiki/Ethereum">Ethereum</a> wallet (cryptocurrency) that also includes support for <a href="https://our.status.im/tag/dapps">DApps (decentralized apps)</a> (web apps in a curated store). Uses the <a href="https://blog.enuma.io/update/2018/08/08/decentralized-application-messaging-with-whisper.html">Whisper protocol</a> for P2P communication. <span class="badge badge-warning">Experimental</span></li>
     <li><a href="https://retroshare.cc">Retroshare</a> - Encrypted instant messaging and voice/video call client. RetroShare supports both <a href="https://www.torproject.org/">Tor</a> and <a href="https://geti2p.net">I2P</a>.</li>
+    <li><a href="https://bitmessage.org">Bitmessage</a> is a decentralized, encrypted, peer-to-peer, trustless communications protocol that can be used by one person to send encrypted messages to another person, or to multiple subscribers.</li>
 </ul>