The big purge of the old widget mechanism

Getting rid of the old widget mechanism files finally gives us a payoff
for all the refactoring. Still a bit of tidying up to do, and we need
to re-introduce the animation mechanisms.

core/modules/widgets/error.js

@@ -1,37 +0,0 @@
-/*\
-title: $:/core/modules/widgets/error.js
-type: application/javascript
-module-type: widget
-
-The error widget displays an error message.
-
-\*/
-(function(){
-
-/*jslint node: true, browser: true */
-/*global $tw: false */
-"use strict";
-
-var ErrorWidget = function(renderer,errorMessage) {
-	// Save state
-	this.renderer = renderer;
-	this.errorMessage = errorMessage;
-	// Generate child nodes
-	this.generate();
-};
-
-ErrorWidget.prototype.generate = function() {
-	// Set the element details
-	this.tag = "span";
-	this.attributes = {
-		"class": "tw-error-widget"
-	};
-	this.children = this.renderer.renderTree.createRenderers(this.renderer,[{
-			type: "text",
-			text: this.errorMessage
-		}]);
-};
-
-exports.error = ErrorWidget;
-
-})();