sixtyforce 2.0 beta 1

This version requires macOS 10.9 (Mavericks) or later.

What's new in this version of sixtyforce:

* Rewrote the majority of sixtyforce in Swift.
* sixtyforce can now download and install app updates.
* Completely rewrote game controller support, adding new controller art, improved element naming and much more.
* Added a completely redesigned interface for configuring game controllers.
* Added support for the Switch Pro controller, Xbox One controller and newer PS4 controllers.
* Worked around a bug in macOS Catalina that caused a warning dialog to appear.
* Fixed a bug that prevented game controllers from registering D-pad diagonal directions properly.
* Fixed a bug that prevented Xbox One controller triggers from working.
* Fixed a bug that prevented files from opening when dropped on the app icon.