Fix #5308 - WidgetSubclassingMechanism not working with widgets that add EventListeners (or logic ?) in constructor (#5382)

* add EventListeners in the render() method instead of the constructor

* scrollable widget: add EventListeners in render() method instead of constructor +

... move logic from constructor to render()

* linkcatcher: add EventListeners in render() instead of constructor

* fieldmangler: add EventListeners in render() instead of constructor

* edit-bitmap: initialise editorOperations in render() instead of constructor

* list-widget: initialise storyviews in render() instead of constructor

* vars widget: execute Widget.call(this) in render() instead of constructor

... not shure what this should do

* Update fieldmangler.js

* Update edit-bitmap.js

* Update linkcatcher.js

* Update navigator.js

* Update scrollable.js

* Update list.js

* Update vars.js

core/modules/widgets/linkcatcher.js

@@ -16,9 +16,6 @@ var Widget = require("$:/core/modules/widgets/widget.js").widget;
 
 var LinkCatcherWidget = function(parseTreeNode,options) {
 	this.initialise(parseTreeNode,options);
-	this.addEventListeners([
-		{type: "tm-navigate", handler: "handleNavigateEvent"}
-	]);
 };
 
 /*
@@ -30,6 +27,9 @@ LinkCatcherWidget.prototype = new Widget();
 Render this widget into the DOM
 */
 LinkCatcherWidget.prototype.render = function(parent,nextSibling) {
+	this.addEventListeners([
+		{type: "tm-navigate", handler: "handleNavigateEvent"}
+	]);
 	this.parentDomNode = parent;
 	this.computeAttributes();
 	this.execute();