Initial approach to a widget based plugin system

Change-Id: I8ad07c817248a0d205ec9eb66f0dc579fbcd7160
diff --git a/dev/demo/plugin-server.html b/dev/demo/plugin-server.html
new file mode 100644
index 0000000..f513b46
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+++ b/dev/demo/plugin-server.html
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+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Plugin demo</title>
+    <link type="text/css" rel="stylesheet" href="/css/kalamar.css" />
+    <script data-main="/demo/plugin-serverdemo.js" src="/js/lib/require.js" async="async"></script>
+  </head>
+  <body>
+    <p>Start the demo server with <code>morbo -l 'http://*:3003' t/plugin-server.pl</code> and open <a href="http://localhost:3003/demo/plugin-server.html"><code>this website</code></a>.</p>
+    <main>
+      <div id="container"></div>
+    </main>
+  </body>
+</html>