overview, appDisplay: add Dash to Ctrl-Alt-Tab

Add the dash to Ctrl-Alt-Tab, add appropriate :focus CSS, and connect
to the popup-menu signal on dash icons.

https://bugzilla.gnome.org/show_bug.cgi?id=618887

js/ui/overview.js

@@ -197,6 +197,10 @@ Overview.prototype = {
         this.dash.actor.add_constraint(this.viewSelector.constrainY);
         this.dash.actor.add_constraint(this.viewSelector.constrainHeight);
 
+        // Translators: this is the name of the dock/favorites area on
+        // the left of the overview
+        Main.ctrlAltTabManager.addGroup(this.dash.actor, _("Dash"), 'user-bookmarks');
+
     },
 
     _onDragBegin: function() {