Unload autosave on turbolinks page render.

We cannot use turbolinks:request-start because this will duplicate code (if a page is first requested by turbolinks and afterwards by a full page reload)

app/assets/javascripts/editor/editor.js.erb

@@ -889,6 +889,7 @@ var CodeOceanEditor = {
         this.initializeDeadlines();
         CodeOceanEditorTips.initializeEventHandlers();
 
+        window.addEventListener("turbolinks:before-render", this.unloadAutoSave.bind(this));
         window.addEventListener("beforeunload", this.unloadAutoSave.bind(this));
         // create autosave when the editor is opened the first time
         this.autosave();