Made GUI modifications and added a Reverse FFT

- The old GUI was falling apart after updating PyQt5 so I reworked the GUI into grids and buttons.
- Added what I'm calling a "Reverse FFT" which takes the output of the FFT(frequency plots) back into sound with sine waves.
I made it in a way to get a cleaner sound so it's not 100% accurate on purpose.

Author: GhostNaN