Toggle with no dataref state

[devleaks]

Hello,

there are a few cases where you have a command and the state of the command is not reflected in dataref. For example, the sim/map/show_current command displays the map on screen, but there is no way to know map is open or not. There are numerous such "toggle" commands. However, it is interesting to reflect the state (off or on) in the button icon.

I suggest we add a toggle type with two icons and switch between the two icons each time the button is pressed. I understand there is not way to "guess" the initial state of the toggle, we assume it is OFF.

Pierre