More scaling option in offsets panel

[fabienBourban]

Would it be possible to have more scaling option in the "Offsets" panel so that he can be used also for EMG and even to test DCs on new hardware.
The idea would be instead of having just those two options: "25.0mV", "50.0mV" we would have "25 mV", "50 mV", "100 mV", "500 mV", "1 V", "2 V", "5 V".

Also like in the example to add a space between the number and the unit like in the EEG panel.