Biquad filter "show response" button should show a graph

[AlisterH]

• Instead of printing a bunch of numbers to stdout and noise.dat, it should display something in the gui, as users have no way of knowing they need to look at terminal output EDIT - I have added a status message saying it was saved to noise.dat, so that at least users can know what happens currently.
• Preferably it should be displayed in a graphical way, not as text.