Implemented basic extra handling (ie. plug-ins in Antville):

* Added global app.data.extras collection and registerExtra() method
 * Defined res.handlers.extra in HopObject.onRequest() handler to provide extra macros
 * Implemented reCAPTCHA for anonymously contacting an Antville member as proof of concept

extra/recaptcha/Global/recaptcha.js

@@ -0,0 +1,60 @@
+// The Antville Project
+// http://code.google.com/p/antville
+//
+// Copyright 2007-2011 by Tobi Schäfer.
+//
+// Copyright 2001–2007 Robert Gaggl, Hannes Wallnöfer, Tobi Schäfer,
+// Matthias & Michael Platzer, Christoph Lincke.
+//
+// Licensed under the Apache License, Version 2.0 (the ``License'');
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an ``AS IS'' BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// $Revision$
+// $Author$
+// $Date$
+// $URL$
+
+/**
+ * @fileoverview Defines the Antville reCAPTCHA Feature.
+ * @see http://www.google.com/recaptcha
+ */
+
+registerExtra("recaptcha", new function() {
+   var key = getProperty("recaptcha.key");
+
+   return {
+      _macro: function() {
+         if (key && !session.user) {
+            renderSkin("recaptcha", {id: getProperty("recaptcha.id")});
+         }
+         return;
+      },
+
+      verify: function(data) {
+         var http = new helma.Http;
+         http.setTimeout(200);
+         http.setReadTimeout(300);
+         http.setMethod("POST");
+         http.setContent({
+            privatekey: key,
+            remoteip: req.data.http_remotehost,
+            challenge: data.recaptcha_challenge_field,
+            response: data.recaptcha_response_field
+         });
+         var request = http.getUrl("http://www.google.com/recaptcha/api/verify");
+         if (request.code === 200 && !request.content.startsWith("true")) {
+            throw Error(gettext("Please enter the correct words in the CAPTCHA box."));
+         }
+         return;
+      }
+   }
+});

extra/recaptcha/Global/recaptcha.skin

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+<script type="text/javascript">
+var RecaptchaOptions = {
+   theme: 'default',
+   lang: '<% site.locale %>'
+};
+</script>
+<script type="text/javascript" src="http://www.google.com/recaptcha/api/challenge?k=<% param.id %>">
+</script>
+<noscript>
+  <iframe src="http://www.google.com/recaptcha/api/noscript?k=<% param.id %>"
+      height="300" width="500" frameborder="0"></iframe><br>
+  <textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>
+  <input type="hidden" name="recaptcha_response_field" value="manual_challenge">
+</noscript>