GApplication: add accessor for DBus information

Provide public access to the GDBusConnect and object path that
GApplication is using.  Prevents others from having to guess these
things for themselves based on the application ID.

https://bugzilla.gnome.org/show_bug.cgi?id=671249

gio/gapplicationimpl-dbus.c

@@ -597,6 +597,17 @@ g_application_impl_flush (GApplicationImpl *impl)
     g_dbus_connection_flush_sync (impl->session_bus, NULL, NULL);
 }
 
+GDBusConnection *
+g_application_impl_get_dbus_connection (GApplicationImpl *impl)
+{
+  return impl->session_bus;
+}
+
+const gchar *
+g_application_impl_get_dbus_object_path (GApplicationImpl *impl)
+{
+  return impl->object_path;
+}
 
 /* GDBusCommandLine implementation {{{1 */