Introduce new manualdownload saver

This saver pops up a modal dialogue giving the user an opportunity to
right click and save the wiki

core/modules/savers/manualdownload.js

@@ -0,0 +1,52 @@
+/*\
+title: $:/core/modules/savers/manualdownload.js
+type: application/javascript
+module-type: saver
+
+Handles saving changes via HTML5's download APIs
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var downloadInstructionsTitle = "$:/messages/Download"
+
+/*
+Select the appropriate saver module and set it up
+*/
+var ManualDownloadSaver = function(wiki) {
+};
+
+ManualDownloadSaver.prototype.save = function(text) {
+	$tw.modal.display(downloadInstructionsTitle,{
+		downloadLink: "data:text/html," + encodeURIComponent(text)
+	});
+	return true;
+};
+
+/*
+Information about this saver
+*/
+ManualDownloadSaver.prototype.info = {
+	name: "manualdownload",
+	priority: 0
+};
+
+/*
+Static method that returns true if this saver is capable of working
+*/
+exports.canSave = function(wiki) {
+	return true;
+};
+
+/*
+Create an instance of this saver
+*/
+exports.create = function(wiki) {
+	return new ManualDownloadSaver(wiki);
+};
+
+})();