Radio On/Off

Currently there is no way to tell if a radio is on/off. When pressing the tangent, it might be better to `showHint` a message saying that the radio is off.

I will begin working on disabling a couple UI elements (channel and frequency) when opening the display when the radio is off. Power buttons will have to be added to the radio dialogs, or the volume rotator should stop at 0 and the radio should be placed in an off state.

Relies on https://github.com/michail-nikolaev/task-force-arma-3-radio/pull/833
Partially solves https://github.com/michail-nikolaev/task-force-arma-3-radio/issues/753