OSX Controller Support

[200sc]

We don't have access to a mac to test on, so controller support hasn't been implemented or tested on a mac. We should resolve this.

[200sc]

Documenting research:
We must interact with OSX's IOHIDManager: https://developer.apple.com/documentation/iokit/iohidmanager_h?language=objc
OSX's kernel will claim all HID devices, which controllers will qualify as, as soon as they are connected to the machine, and require that they are read from via IOHIDManager.

We could either attempt to manually use IOHIDManager's API, or use libusb's hidapi: https://github.com/libusb/hidapi