shell-app: Add "discrete_gpu" option when launching apps

And adapt existing callers to the new API. This will allow us to
implement a way to launch applications on the discrete GPU for systems
where an "Optimus" system exists.

https://bugzilla.gnome.org/show_bug.cgi?id=773117

js/ui/components/autorunManager.js

@@ -64,7 +64,8 @@ function startAppForMount(app, mount) {
 
     try {
         retval = app.launch(files, 
-                            global.create_app_launch_context(0, -1))
+                            global.create_app_launch_context(0, -1),
+                            false)
     } catch (e) {
         log('Unable to launch the application ' + app.get_name()
             + ': ' + e.toString());