Allow cropping of signal

[samyk]

Feature request

Allow cropping of a signal using a drag+drop of a selection box with a button and hotkey to crop that portion of the signal, and the ability to save it as a new file. It would be nice if it included the sample rate in the filename by default.

To get an idea of how this would look, I use an audio tool called Izotope RX which essentially has this same functionality on waveforms (though is specifically meant for audio)