Add httpNodeMiddleware option

Closes #631

Enables custom middleware to be inserted in front of all HTTP In
nodes.

settings.js

@@ -125,6 +125,15 @@ module.exports = {
     // http request node.
     //httpNodeProxy : { host:"myproxy.acme.com", port:8080 },
 
+    // The following property can be used to add a custom middleware function
+    // in front of all http in nodes. This allows custom authentication to be
+    // applied to all http in nodes, or any other sort of common request processing.
+    //httpNodeMiddleware: function(req,res,next) {
+    //   // Handle/reject the request, or pass it on to the http in node
+    //   // by calling next();
+    //   next();
+    //},
+    
     // Anything in this hash is globally available to all functions.
     // It is accessed as context.global.
     // eg: