Use the new GApplication support in ShellApp to create the application
menu. Supports plain (no state), boolean and double actions.
Includes a test application (as no other application uses GApplication
for actions)
https://bugzilla.gnome.org/show_bug.cgi?id=621203
GDBusActionGroup and GMenuProxy are new objects in GIO 2.32 that
help with accessing menus and actions of remote applications.
This patch makes it possible for the shell to associate an
application with a dbus name and from that a GMenu, that will
be shown as the application menu.
https://bugzilla.gnome.org/show_bug.cgi?id=621203