Add warning notification when viewing a document on a data: uri

The intent is to handhold the user through their first save+verification

core/modules/utils/dom/modal.js

@@ -0,0 +1,40 @@
+/*\
+title: $:/core/modules/utils/dom/modal.js
+type: application/javascript
+module-type: utils
+
+Modal message mechanism
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var Modal = function(wiki) {
+	this.wiki = wiki;
+};
+
+Modal.prototype.display = function(title) {
+	var wrapper = document.createElement("div"),
+		template,renderer;
+	template = "$:/templates/ModalMessage";
+	renderer = $tw.wiki.parseTiddler(template);
+	renderer.execute([],title);
+	renderer.renderInDom(wrapper);
+	$tw.wiki.addEventListener("",function(changes) {
+		renderer.refreshInDom(changes);
+	});
+	wrapper.addEventListener("tw-close",function(event) {
+console.log("Got tw-close event");
+		document.body.removeChild(wrapper);
+		event.stopPropogation();
+		return false;
+	},false);
+	document.body.appendChild(wrapper);
+};
+
+exports.Modal = Modal;
+
+})();