Started refactoring TiddlyWeb syncer into generic syncer + TiddlyWeb adaptor

The refactored plugin is `tiddlyweb2` for the moment. The idea is to be
able to use the same syncer with a different adaptor for syncing
changes to the local file system.

core/modules/utils/dom/http.js

@@ -0,0 +1,65 @@
+/*\
+title: $:/core/modules/utils/dom/http.js
+type: application/javascript
+module-type: utils
+
+Browser HTTP support
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+/*
+A quick and dirty HTTP function; to be refactored later. Options are:
+	url: URL to retrieve
+	type: GET, PUT, POST etc
+	callback: function invoked with (err,data)
+*/
+exports.httpRequest = function(options) {
+	var type = options.type || "GET",
+		headers = options.headers || {accept: "application/json"},
+		request = new XMLHttpRequest(),
+		data = "",
+		f,results;
+	// Massage the data hashmap into a string
+	if(options.data) {
+		if(typeof options.data === "string") { // Already a string
+			data = options.data;
+		} else { // A hashmap of strings
+			results = [];
+			$tw.utils.each(options.data,function(dataItem,dataItemTitle) {
+				results.push(dataItemTitle + "=" + encodeURIComponent(dataItem));
+			});
+			data = results.join("&");
+		}
+	}
+	// Set up the state change handler
+	request.onreadystatechange = function() {
+		if(this.readyState === 4) {
+			if(this.status === 200 || this.status === 204) {
+				// Success!
+				options.callback(null,this.responseText,this);
+				return;
+			}
+		// Something went wrong
+		options.callback(new Error("XMLHttpRequest error: " + this.status));
+		}
+	};
+	// Make the request
+	request.open(type,options.url,true);
+	if(headers) {
+		$tw.utils.each(headers,function(header,headerTitle,object) {
+			request.setRequestHeader(headerTitle,header);
+		});
+	}
+	if(data && !$tw.utils.hop(headers,"Content-type")) {
+		request.setRequestHeader("Content-type","application/x-www-form-urlencoded; charset=UTF-8");
+	}
+	request.send(data);
+	return request;
+};
+
+})();