Support multiple settings profiles

I use SSR for recording with at least two different sets of settings (desktop recording vs twitch streaming), and changing between them was a pain in the butt (in particular, relocating the stream key every time... ugh).

So I scratched my itch and wrote this up. Now SSR itself tracks the different settings you want to save, and the user can name these profiles as desired.

The GUI formatting might be up to snuff, but it's certainly not terrible. (This is my first ever graphical anything, so I did my best imitation of your code, combined with a dash of Qt documentation.)