Make entire switcher work as a piano, instead of just the first seven apps (and refactoring)

Although I did end up refactoring and reorganizing the code quite a bit (really sorry about that, honestly) in order for it to compile and build properly on my system, the major change was **the normalization of notes**. Instead of calculating an app's note (noteIndex) based on its location relative to the first seven apps, this version calculates the note based on the entirety of the apps in the switcher. If there are just seven apps, each should be one of the seven notes. If there are fourteen apps, every two will be identical, with every set of two playing a single note.

In addition, I added a tiny .gitignore and made some of the naming consistent (such as the tweak name sometimes showing up as lowercase, sometimes uppercase, etc).

I really loved your tweak, and I hope you like these changes! Feel free to let me know otherwise, and I can submit a pull request with a preferences pane to control this version and the last.