Indicates whether the feature can be either on or off, without any other states. This is used by the tool bar and
menu-bar menus to determine whether the feature's enable/disable button or menu item should be displayed with an
indicator that it's either on or off. In the case of a menu the indicator is a check box. In the case of a tool
bar button the indicator is a dot above the button.
true if the feature has only two states, otherwise off.