Suggestion: Show amplitude/frequency plots by default

[samyk]

Running latest 200ea4eb73defdba7b5c07757a637cef3e9d80a5 on macOS 10.12.1

Suggestion: It would be nice for the amplitude/frequency plots to show up by default. I'd expect them to be 'checked' in the right-click menu and then click again to disable the plot (currently I don't think you can remove a plot once added).

Also, it would be nice if the plots were all in the first right click menu, rather than having to right click -> Add derived plot -> Add [whatever] plot