Scope: change y-axis range

[tlecomte]

Unlike other visualizations, the scope has no setting to adjust the y-axis range. Many times, the input signal has a very low amplitude, which makes it hard to see in the scope. On the other hand, other visualizations such as the FFT spectrum can be used for such small signals because of the y-axis settings.

We could add the y-axis range setting to the scope.