refactor: rewrite Module as an ES6 class

Drop the old browser-side `Class.extend()` helper and make `Module`
a native class, matching the earlier `NodeHelper` rewrite.

Author: KristjanESPERANTO

defaultmodules/newsfeed/newsfeed.js

@@ -148,7 +148,7 @@ Module.register("newsfeed", {
 			}
 			return Promise.resolve(wrapper);
 		}
-		return this._super();
+		return Module.prototype.getDom.call(this);
 	},
 
 	//Override fetching of template name

index.html

@@ -50,7 +50,6 @@
     <script type="text/javascript" src="js/logger.js"></script>
     <script type="text/javascript" src="translations/translations.js"></script>
     <script type="text/javascript" src="js/translator.js"></script>
-    <script type="text/javascript" src="js/class.js"></script>
     <script type="text/javascript" src="config/basepath.js"></script>
     <script type="text/javascript" src="js/module.js"></script>
     <script type="text/javascript" src="js/loader.js"></script>