add preprocessor for RST docs, see #2461 and #2431

The idea is to filter the sources, replacing @<var>@ occurrences with
the mapping for <var> (which is currently hard-coded). @@ -> @. In order
to make this work, I had to move the doc sources one directory down
(into akka-docs/rst) so that the filtered result could be in a sibling
directory so that relative links (to _sphinx plugins or real code) would
continue to work.

While I was at it I also changed it so that WARNINGs and ERRORs are not
swallowed into the debug dump anymore but printed at [warn] level
(minimum).

One piece of fallout is that the (online) html build is now run after
the normal one, not in parallel.

akka-docs/rst/scala/code/docs/camel/Consumers.scala

@@ -0,0 +1,73 @@
+/**
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package docs.camel
+
+import language.postfixOps
+
+object Consumers {
+  object Sample1 {
+    //#Consumer1
+    import akka.camel.{ CamelMessage, Consumer }
+
+    class Consumer1 extends Consumer {
+      def endpointUri = "file:data/input/actor"
+
+      def receive = {
+        case msg: CamelMessage ⇒ println("received %s" format msg.bodyAs[String])
+      }
+    }
+    //#Consumer1
+  }
+  object Sample2 {
+    //#Consumer2
+    import akka.camel.{ CamelMessage, Consumer }
+
+    class Consumer2 extends Consumer {
+      def endpointUri = "jetty:http://localhost:8877/camel/default"
+
+      def receive = {
+        case msg: CamelMessage ⇒ sender ! ("Hello %s" format msg.bodyAs[String])
+      }
+    }
+    //#Consumer2
+  }
+  object Sample3 {
+    //#Consumer3
+    import akka.camel.{ CamelMessage, Consumer }
+    import akka.camel.Ack
+    import akka.actor.Status.Failure
+
+    class Consumer3 extends Consumer {
+      override def autoAck = false
+
+      def endpointUri = "jms:queue:test"
+
+      def receive = {
+        case msg: CamelMessage ⇒
+          sender ! Ack
+          // on success
+          // ..
+          val someException = new Exception("e1")
+          // on failure
+          sender ! Failure(someException)
+      }
+    }
+    //#Consumer3
+  }
+  object Sample4 {
+    //#Consumer4
+    import akka.camel.{ CamelMessage, Consumer }
+    import scala.concurrent.util.duration._
+
+    class Consumer4 extends Consumer {
+      def endpointUri = "jetty:http://localhost:8877/camel/default"
+      override def replyTimeout = 500 millis
+      def receive = {
+        case msg: CamelMessage ⇒ sender ! ("Hello %s" format msg.bodyAs[String])
+      }
+    }
+    //#Consumer4
+  }
+}