Implement support for some basic embed options for work sheets via LTI

This commit also fixes an issue with the flash messages being positioned too high and displayed for too long

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

@@ -110,6 +110,10 @@ configureEditors: function () {
 
   // The event ready.jstree is fired too early and thus doesn't work.
   selectFileInJsTree: function(filetree, file_id) {
+    if (!filetree.is(':visible'))
+        // The left sidebar is not shown and thus the filetree is not rendered.
+        return;
+
     if (!filetree.hasClass('jstree-loading')) {
       filetree.jstree("deselect_all");
       filetree.jstree().select_node(file_id);
@@ -224,6 +228,11 @@ configureEditors: function () {
       // remove last (empty) that is there by default line
       document.removeLines(document.getLength() - 1, document.getLength() - 1);
       editor.setReadOnly($(element).data('read-only') !== undefined);
+      if (editor.getReadOnly()) {
+        editor.setHighlightActiveLine(false);
+        editor.setHighlightGutterLine(false);
+        editor.renderer.$cursorLayer.element.style.opacity = 0;
+      }
       editor.setShowPrintMargin(false);
       editor.setTheme(this.THEME);
 
@@ -458,7 +467,7 @@ configureEditors: function () {
 
     var editor = this.editor_for_file.get(file);
     editor.gotoLine(line, 0);
-
+    event.preventDefault();
   },
 
   augmentStacktraceInOutput: function () {
@@ -722,6 +731,7 @@ configureEditors: function () {
     this.initPrompt();
     this.renderScore();
     this.showFirstFile();
+    this.resizeAceEditors();
 
     $(window).on("beforeunload", this.unloadAutoSave.bind(this));
     // create autosave when the editor is opened the first time