Revert "Use menu model for left GtkMenuButton."

This reverts commit dc5987a12dc5547f92600d6d95c77425c178e8a4.

Conflicts:
	app.glade
Revert "Use menu model for right edit menu."

This reverts commit cd383f77a9e8f630e84da2c3ad4ad08048d8447e.

Conflicts:
	app.glade
Typo
Use set_app_menu() only for HeaderBar mode.
Use 16 pixel icon for ST button.